Just upgraded to Mountain Lion from Snow Leopard, and just experienced this whole hang with the cursor moving, iTunes playing, and nothing else working for the first time. I had a few weird quirks on occasion in Snow Leopard where my screen would go all white or black. Not sure if that is related... But seriously, Apple? I skipped Lion to avoid bugs like this!

Heh.... Looks like Mountain Lion is having the same problems, except worse: it's affecting audio, not just video.

http://reviews.cnet.com/8301-13727_7-57489874-263/sound-stuttering-after-mountai n-lion-installation/

I did not like Lion at all, I did a clean install on my Mac Mini, and have had zero issues so far. In fact everything seems to work much smoother and quicker. Plus now I can open several videos with out them crashing, before with Lion I could open maybe one and that was it. So far so good.

I put Mountain Lion on my 2008 iMac, and, so far, things have gone well.  As Gandalf said, it is smoother and quicker than Lion.  Aside from not crashing (yet), none of the other nasty Lion symptoms have appeared:  excessive heating of the case, sluggish desktop effects (after 3-4 hours of use).

It's still too early to know if this release solves our problems, but I hope that everyone will continue to post their progress.

Maybe what I'll do is install ML on a partition and migrate the data over and see how it works.

I installed ML on a small partition for testing.  I wasn't going to fully commit to it after this Lion debacle. 

I've still got a Leopard 10.5.8 partition to fall back on if things begin to go badly.

OK question:  I just installed ML on a new partition, and, of course, am having problems- this time it goes to sleep after about 20 minutes whether I'm doing something or not, and then won't wake up.  Here's an overview of that problem: https://discussions.apple.com/message/19238767#19238767

So I decided to switch back over to Lion and see if the same thing happened.  Interestingly, even though I have no programs open and am not using it at all, right at about 20 minutes the activity monitor showed a massive increase in CPU usage - literally from NOTHING suddenly to 100% or more.

In ML when the sleep thing happens, there is no noticable change in the CPU usage in Activity Monitor.

But is it possible that something is happening 20 minutes after booting that causes the kernel to exert a huge amount of CPU usage in Lion, but in ML manifests differently by going into Sleep mode?

Joey,

I don't know why that would be happening to you----sleeping after 20 minutes.  I've never seen that happen in Mountain Lion since I've installed it.  Your machine appears to be very similar to mine, too.  Mine is Core 2 Duo, early 2008 iMac, 4GB ram.

I will launch Activity Monitor and watch closely what happens today.

One would think that a clean installation would be the way to go.  I was lazy and simply launched the App which just installed over the top of Lion.

Studio K: I can't read the above message could you please retype it! LOL

I totally agree, I installed ML over Lion and still had some minor issues so I went the clean install route with my 2012 Mac Mini. Now on my Macbook Pro, I didn't have any issues with Lion and just installed it over the top of Lion and have had zero issues so far as well.

So how do you do a clean reinstall. Now I have not upgraded to mt. lion, and I have a 24" imac that is having the same problem as most, it keeps crashing daily. It looks a lot like the screen shots I have seen with the video being broken up all over. I took it to the Apple Store and they replaced the hard drive for hefty price. And I am still having the problem. The other problem is the optical drive has stopped working, so could I even do a clean reinstall. I am using OS 10.7.4. The Apple Genius said that replacing the hard drive took care of the problem, and yet, it still exists. Was going to take it back in, is there somethig I should be telling the genius about this problem, or should I just try the clean reinstall. Of course I probably need an optical drive. This computer is only 3 yrs old, should I even be having these problems? The problem does seem coincide with the install of Lion, I am very frustrated by all this.

RaiderTodd,

I believe that it's possible to clean instal from a usb flash drive.  I used Disk Utility to place the installation .dmg file onto the flash drive, which makes it bootable and otherwise behave just as the optical disc would.

I did this with Snow Leopard and have not tried it with Mountain Lion.

The .dmg for Mountain Lion is located inside the App (right click-->show package contents).  Find that .dmg file (called installESD.dmg or something like that), then copy it to your desktop.  Launch Disk utility and put it onto the Usb.

I don't remember the full procedure, but it's easy to find on Google.

Thanks Studio K, I will give that a try.

When I get my hang up I do a three finger swipe to chage spaces and it unlocks.

Very frustrating if it turns out this is an OSX update issue.

I've posted in this thread before.... knock on wood, but I have yet to have this issue on my 2007 iMac since upgrading to Mountain Lion which I did the day it was released.

Hi,

Unfortunately I can confirm this problem indeed exist also in Moutain Lion, and as you write even worse.

After updating my iMAC 27" I7, I have this problem several times pr week. I'm using my computer work wize why I always are very strict about latest updates and no "******" software installed, only sw with valid license.

I have googled the problem for several hours, both in Mac Support and on other MAC communities on the www, but still haven't found one single thread having the right solution.

@Apple - could you please fill in on this!

br,

Nicolai