I did some tests and in my case it seems is connecting the external display what causes the problems, which in my case are basically lack of precission using the mouse. (Logitech MX 1000)
I couldn't appreciate any difference whether iTunes is running or not.
I also couldn't find any difference if both displays were active or just the external one (i.e. MBP's lid closed)
The issue is restricted to the mouse, the trackpad works fine in every set up I tested
I returned the Logitech G500 Mouse as I found the tracking to not be as good as I hoped it to be (regardless of the current OS X10.7 mouse tracking issue), and found the shape of the mouse to not be optimized for my preference / hand size.
I exchanged it for a Razer DeathAdder as it received really good reviews and is fully Mac compatible with their drivers / software. I am impressed. It physically feels better in my hand and, imo, the tracking is noticeably better than the G500. I have polling and DPI on max with all defaults except mouse button 3-5 mapped as passthrough. I noticed the software disables mouse acceleration by default.
iTunes still, for me, causes mouse tracking issues when I am extending my laptop desktop across two other monitors. It is just a lot more tolerable in my situation as it is slight and not as frequent. Less fighting with the mouse now and more just doing my work (wrist feels better).
Any ways, if your experiencing similar issues as I and others here have described and you are fed up with it, I would recommend that you try out the Razer DeathAdder mouse. Make sure that you purchase from a store that has a proper "no questions asked, full refund" return policy in case this mouse is not suited for you for whatever reason.
I use two mouses [sic]. I use the Kensington 4-Button USB Expert Pro Trackball on my left hand and a the Logitech MX series on my right (I've used 3 different MX series mice. The larger the better for most anyone). I've not only found that having two mice cuts the amount of use on one single hand down by 50%, but that I even have preferences for tasks based on these two types. It took me a bit to move to get use to a trackball and my left hand, but it's so completely natural now, it's solved all my issues with CTS. That being said, the trackball is better with the tracking and skipping issues as well, but doesn't fix them.
It's simply a graphics card issue. We're all overloading the GPU on our systems, no way around it really except to cut back on GPU use and iTunes is the secret tipping point. I'm looking forward to the new MBP's coming out soon with hopes of some extra GPU performance. However, with talks of being in the air style casing, it's unlikely we'll see any massive GPU upgrades *sigh*. I've just been using Spotify over iTunes myself and haven't been too put off by this.
Anyway, just a couple pointers.
Thanks for the tip (Spotify), going to buy it now and give it a go. I think the hardware (CPU/GPU) for my mbp is more than capable for this type of task. I believe it's some buggy issues with iTunes (software) that is causing the symptoms for me. Maybe we expect too much from our Macs, it's OS and applications? I certainly hold it to higher standards when compared to Microsoft and Linux/Unix for desktop / user experience, and to DELL / HP for hardware.
Good to hear clearing the NVAM worked for you (it made no difference for me).
Resetting your Mac's PRAM and NVRAM:
I am having almost all of the Magic Mouse problems others have reported. It's like a crazy person is taking over the mouse with clicks that weren't caused by me, erratic mouse movements, jumping of cursor to a far corner of the screen, swipes to second programs that are open, the whole works. It started with Lion and hasn't yet been fixed by Apple. My problem has nothing to do with a second monitor. I don't have one. I rarely open itunes, and don't keep it running. I have no doubt that the problem is in the operating system, not hardware, because everything worked perfectly in Snow Leopard, before all the IOS features were added in Lion. Hopefully, at some point Apple will address this issue.
the wireless apple mouse, trackpad and keyboard that worked fine with my 24" imac randomly lose connection and constantly move erratically when i use them with my new 17" mbp. i been guessing it was a bluetooth thing with the new laptop because all 3 wireless devices worked without incidence on my old plastic imac. i do have an hdmi cord to an external monitor hooked up that i didn't use with the old comp. when i get a chance i'll check to see if the mouse pointer behaves right with the ext. monitor and hdmi cable unplugged.
good luck i'll report soon.
FWIW, I read thru this thread looking for a solution to the same issue. iMac 27 with a Magic Mouse and Trackpad. The Trackpad was working fine but the Magic Mouse cursor was balky/jumpy. This started just recently. In addition, my Cropmark LMP Bluetooth Keypad would no longer connect. I have an iMac 24 with the same setup and no issues. Also. my Airport Extreme is on the desk next to my iMac 27. On a lark (think I read this somewhere), I edited the setup on the AE and change the channels from Automatic to a specific channel (both 2.4 and 5.0 gHz). Problem solved.
Still haven't found a solution for the issues that I'm encountering.
After further investigations, it seems to be related most likely to downsized or buggy support for the mice I'm using.
Here, it's definetively no Bluetooth or iTunes side effect, as I don't use any Bluetooth devices or iTunes on this machine (MacPro 3,1).
Tried 4 different cable bound mice (Logitech, Macally, Microsoft, Elecom), each showing a different erratic behaviour, while my favourite mouse (Elecom Scoop Node) unfortunately behaves worst.
This wasn't the case under Snow Leopard, where this mouse worked flawlessly.
Unfortunately, I'm professionally using software that relies heavily on 3-button mice with a scrollwheel, so I cannot use any Apple input device but am dependant on OSX's native mouse driver support (Magic Mouse isn't usable professionally due to its poor ergonomics and the dust problems with the scrollball).
In the meantime, I came to 2 possible reasons:
buggy support for 3rd party input devices within Lion or an issue with USB current supply, as I seem to notice better behaviour of the Elecom mouse when disconnecting a software protection dongle from the keyboard's 2nd USB port, but this cannot be either a workaround nor a solution. (All other USB devices are connected to an active USB-Hub).
When I boot into Bootcamp's OS selection screen, I'm no longer able to use the Elecom mouse to select the startup OS, as the cursor moves exclusively horizontally at the screen heigth where the cursor appears at the beginning (~150px *below* the OS icons).
In this state, the input of the Wacom tablet is recognized correctly.
If I change to another mouse, it's movement is also recognized correctly.
(btw, the Wacom also gives errors while working in OSX-Lion).
Once booted into Win7, there aren't any further issues with the Elecom or other mice, indicating that it is definetively an OSX bug.
I'll issue another bug report to Apple and when this issue will not be resolved with 10.7.4 I'm downgrading back to Snow Leopard.
i've encountered a similar, if not the same issue.
my hardware setup: Macbook 13" (2010), Wireless Keyboard, Magic Mouse.
my mouse started jumping around and my Wireless Keyboard didn't connect.
so i figured out what i've done.
yesterday i set up my iPad2 as a second screen using wifi and the iScreen app - but i worked perfectly fine.
i've also connected an internet stick yesterday without using either my wireless keyboard nor my magic mouse as i was just surfing around on the couch. the only issue i had yesterday was that my pointer disappeared from time to time (using the built-in trackpad).
this morning - no problems at all - until i went to work...
when i got in the office this morning, woke my macbook 13" and connected it to my new display, the mouse started jumping.
i disconnected the display as i thought that caused the problem, but the mouse still kept on jumping - i could clearly see this when i lifted it off my desk and put it back.
i deleted magicprefs, i disconnected both mouse and keyboard (since the keyboard wasn't able to connect), switched batteries, checked the sensor and rebooted twice - with no results...
what worked for me:
after some research i tried the VRAM reset (for the exact procedure, please check the Apple support site) and afterwards my MacBook didn't seem to boot.
then i figured out that i had to select the bootdrive -> you do that by restarting your computer while holding the x-button and then select the drive containing Mac OS X. It took like forever, but in the end, I was able to set up my Bluetooth devices and they're up and working as before.
Powerpoint erratically and inexplicably scrolls through 10 or 12 slides when I use my new wireless Apple Magic Mouse. Very, very annoying, and a problem that other users have been discussing since at least 2010.
MacBook Pro 17" (early 2011); Mac OS X version 10.7.3;
Apple Magic Mouse (MB829LL/A);
Microsoft PowerPoint for Mac 2011, Version 14.1.4