Mouse skipping problem when external display connnected

Just got new 27" iMac and have a second monitor connected with the MiniDisplayPort-to-DVI adapter. My mouse skips around the screen (freezes for a split second, but does it often). Very annoying! Hope Apple comes up with a fix soon.

UPDATE: After numerous calls and running several tests for the Apple techs, including a display timing dump, the communication stopped. I emailed the rep at least 6 times over the course of a month, with no responses whatsoever.

I finally started a new case and the nice tech apologized, looked up all the previous info, had me run another system dump and promised that she would get back to me with some engineering results in about 2-3 days.

Here it is 9 days later, and 4 emails later, and there's be no response whatsoever!!! ***? Do I start yet another case or start calling the consumer reports news teams?

It's obvious that it's not a totally isolated problem, but for well over 2 months now, I've been consistently losing productivity and wasting time with no solution.

I want Apple to send me a new machine or a new monitor (if not a real software solution) and stop dodging this issue.

As a pro Apple user since 1978, this just stinks!!!

Please keep us posted on what's going on with your talks with Apple.
I've just opened a bug report on Apple's feedback site, hope it helps somehow.

Well, 2 weeks now and still no response from Apple Support on the second case for this issue. However, on my last email over the weekend, I cc'ed Mr. Jobs, and now I have a support manager from the executive office calling me to help, so while we haven't crossed paths yet, I hope to make some headway very soon. I'll report back and hopefully whatever we find out can help others. I truly hate being frustrated with Apple (a loyal pro user since 1978 here), so I hope this all works out as I'm losing productivity/$ as we speak. :]

I'm with ya Mark...same problem here with a 27" iMac and 2nd display. It's got the ATI Radeon HD 4670 graphics card and MiniDP out. Really annoying and cripples my work flow...have to disconnect the second monitor to make it stop which slows me down considerably. I read that updating to 10.6.2 was supposed to fix this issue, but no such luck. We're all aware that new products will have issues, but for Apple just to ignore their customers is plain bad business. What happened to "Best Customer Support" in the business?!?

Also experiencing this issue on the new 27" iMac. Using a wireless USB mouse. The apple bluetooth keyboard that came with the iMac also lags (I guess it could be the whole system). The external monitor is connected via a mini display port to DVI adapter.

I seriously did not expect using an external monitor to be an issue in this day and age...

This happens for me as well, and also especially frequently on external displays, unless I am imagining things. To me, it is always due to intensive wireless network traffic. It goes away completely if there is no wireless network traffic, and get increasingly problematic as I download things. This applies to any traffic; watching YouTube, listening to web radio, anything and everything.

That, in itsef, is an annoying issue that should not even be there, but at least I know what's causing this mouse jerkiness (never when using the touchpad though) for me. It is resolved for me by using a wired connection, or minimizing the wireless traffic.

I hear this can also be caused by active Bluetooth devices, or perhaps even if the mouse itself is a Bluetooth mouse.

Message was edited by: Jonas N

Jonas N - I think this is a different issue. The mouse "lag" I am experiencing happens in consistent intervals (every 3 seconds or so), and is still present when airport and bluetooth are disabled.

I'm having the same issue. I use my MacBook Pro with the screen closed and an Apple 24" Cinema Display attached using the Apple DVI Adapter (The older one, not the new one with the iSight camera build in). As I'm using the computer I'll periodically get the mouse hesitation issue. Seems to be when the processor is under even a tiny bit of load. When I use the MBP without an external monitor attached, it works great, no mouse skipping issues at all.

Through the research that I've done, this issue seems to only effect the following computers:
1. The computer must have a Mini DisplayPort.
2. There must be a monitor attached to the Mini DisplayPort using a DVI adapter. This monitor may be used as the computer's only monitor or as a second display.

If anyone has the mouse skipping/slowing/bad tracking issues who's computer does not match the definition in 1 & 2 above, please post. I believe this is a poorly written Mini DisplayPort driver issue in Mac OS X.

I'm curious if anyone has this issue using the VGA adapter. I'm tempted to try that rather than the DVI one.

WOO! Went to the Apple Store today and exchanged by DVI adapter for a VGA one. My second monitor now with NO keyboard mouse lag! Things look a bit fuzzy on my 2nd monitor now... but that just might be in my head.

I too swapped my MiniDisplayPort-to-DVI for the MDP-to-VGA with great success. No more mouse freezing or skipping, still has good resolution, but not quite as high of quality picture since it now has to convert it from digital to analog before sending the signal. Pretty negligible difference unless you NEED a high(er) def second display. Thanks Mayobutter!

Me too. Brand new 27" iMac, ASUS 23" secondary monitor. Bought the min display port to DVI dongle, to replace the perfectly good mini-DVI to DVI dongle from my two year old iMac (thanks Apple for needlessly swapping around these teeny little ports - a way to churn your customers for dongle sales?)

At any rate - yes, it started mouse lagging - which is what brought me to this thread. Read with interest the wireless issue - tried that (switched from airport to ethernet connection) - no difference. Then I noticed that it only happened when the external display was off. I turned it on, and moused over to it - smooth tracking, then moused back to the main display and tracked in circles - perfectly smooth. Switched off the external while tracking in circles and the problem reappeared. Then went away again when I turned external on. Etc etc. Very repeatable.

This issue is definitely real, but from the discussions here varies slightly from user to user. Definitely related to the external display. Hoping for a software fix on this, as I would like to be able to power down the external monitor when not needed, and still use my mouse!!

To the OP who started two cases with apple tech support. Suggest you keep a hard copy of this thread incase the moderator makes it 'go away'. Something is fishy here, and the silence from apple is telling.

Spoke with an apple rep who checked his database, and 'there was nothing there on this issue' - however after working with me, and reading this thread he agreed that it did seem to be real and he was forwarding it to the engineers.

I have since noticed that my displays behaviour (skips when external display is powered off) was not present when booted into WinXP natively. Seems to suggest a software issue - that should be fixable by a patch - maybe. Software anyways.

If it helps the engineers, I believe that the mouse cursor tracking/hesitation issue happens when the processor is under some load. For example, if you click an application to open it, you might see the cursor hesitate while you're moving it around. If there is any truth to my finding, then it suggests that perhaps some other processor is periodically loading down the processor, thus causing the cursor tracking issue.