Has mountain lion screwed anyone else's iMac up?
Yes, of course, but as that is not normal, that's not a productive question. Most likely, you have some incompatible third-party software installed, though it could be something else as well. What do you mean by "freezing?"
For some general troubleshooting advice, see Understanding upgrade nightmares.
I am having the exact same issue. Since installing Mountain Lion, the entire system will, rather randomly, freeze. By freeze I mean no keyboard strokes or combinations of strokes do anything to unfreeze the system, nor does the mouse do anything. The only way to get back in is to do a hard reset. The freeze is occuring at least once per day.
Try doing some basic maintenance.Do a backup, using either Time Machine or a cloning program, to ensure files/data can be recovered. Two backups are better than one.Run Disk Utility/Repair Permissions (Applications/Utility Folder). Run until it reports no errors. If there is a recurring error, see the article on what permission errors can be ignored.
Restart the computer holding down the command - option/alt - P - R keys before the grey screen appears. Continue to hold until you hear the startup chime for the second time.
Try an SMC reset. The article covers when this is required, but doing this will not affect anything.
If you are still experiencing problems after that post what is happening (specifics) and someone can try to help you.
FWIW, I have been encountering the 'random freeze' issue for months. I have:
1) deleted old/obsolete/unused software
2) run Disk Utility to confirm no issues with my drive
3) Reset the NVRAM and PRAM
4) Reset SMC
5) Turned off Bluetooth altogether
6) Run the machine in Safe Boot mode only.
None of these workarounds fixed the issue. In desperation I performed a clean install of 10.8.3. Four days on and I have started to encounter the 'random freeze' again.
From everything I have read on these forums it is not a hardware issue, it is occurring with ML across the range of Apple hardware.
I am using a mid-2007 17" iMac with 4GB RAM. My wife was inclined to upgrade to a new Mac but reading these forums it appears that even some new machines are encountering the same problem.
At this point i am trying to find a means of downgrading to Lion but that is easier than it sounds - in the US you can call a number and pay for a code to download Lion from the App Store. It appears that option is not available in Australia (where I am).
I have been a Mac user since our first home computer was a beige box back in the mid-80s. This is the first time I have genuinely felt seriously about getting rid of my Mac altogether. This issue is detailed multiple times throughout these forums yet to date there appears to be no acknowledgement of the issue by Apple, or any confirmed fix.
At present I have an iMac which is essentially crippled yet in order to revert to a previous version of software I now have to come up with some sort of work around.
This issue needs to be sorted properly, and soon.
Yep. Wish I'd never installed it. Running it on an older imac (mid 2007 model) Never had any issues with it before. Now it freezes all the time, has issues with iTunes and it's getting very very hot. This machine is my baby and I need it to make my living as a graphic designer. Taking it in to NextByte tomorrow to have them revert back an earlier OSX. What a total waste of time and money. It seems that so many peeps are having the same issues with me on their older macs - Apple are being dishonest when they state that Mountain Lion is campatable with older macs. If you're thinking about it, DON'T UPGRADE!!!
This issue was resolved for me by replacing my graphics card. It's been around four months since the graphics card was replaced and the freezing issue has not recurred. While the Genius Bar couldn't replicate the issue while in their custody, the printout I took from the terminal window pointed to the graphics card being the issue.