I've upgraded to 10.6.2 and still encounter the same CPU usage % in the 125%-135% range when watching anything Flash related. Video on Hulu is choppy when played in full screen mode.
We've also encountered a general slow down in overall system performance when we've used it for more than a few hours, especially making movies in iMovie. We too have had problems with screen flickers and PhotoBooth going black.
I'm very concerned about all of these issues and am wondering if it's time to start looking at a replacement machine.
I don't know what to tell you guys still having the problem after installing 10.6.2. I had the identical issues since getting my iMac 27 w/ 8 GB RAM, 3.06 GHz.
The problem was ******* me off so badly that I would literally hit "check software update" about every couple of hours. I was probably one of the first to see it come up, although when I googled 10.6.2, it appears Apple had released it an hour earlier. Note this bullet point, from the APPLE site, as to what 10.6.2 aims to do (amongst several other things):
"this update addresses video playback and performance issues for iMac (21.5-inch, Late 2009) and iMac (27-inch, Late 2009) computers that may occur in some situations while AirPort is turned on"
For those of you who directly plugged in the cable to your computer and turned off airport, that is why you resolved the problem (hardly a solution for us people whose computer is not at the router). In any event, all I can tell you is my video problems are gone since updating.
For those of you whom have downloaded 10.6.2, please confirm that you actually did the update by clicking on the Apple at top left of screen, click "about this mac" and verifying that ver 10.6.2. I know that sounds stupid, but mine actually got hung up and I had to do a hard repower after downloading, and saw that 10.6.1 was still running. Once I clicked for a software update, it recognized I had already downloaded it and then from there powered down and upgraded without incident.
Upgrading to 10.6.2 seems to have worked for me as well. I also found that toggling Airport on/off resolved the problem when I was running 10.6.1, although that seemed to bother my AppleTV sometimes (would get "Video Format Not Recognized" messages unless I restarted the computer or AppleTV). All seems to be resolved since I upgraded last night.