I'm having the same issues!!! My old 2006 20"iMac worked perfectly. Upgraded to the highest specs available in January to a iMac 27" 3.2GHz Intel core i5, with 8GB's of ram and I'm having the same issue. Will try installing the DivX codec pack, hopefully that works.
Thanks for posting your solution, I hate when I find threads on the same issue I'm having, and the poster just replies "Fixed it" without sharing.
Gonna try your suggestion now.
Installing the DIVX codec pack fixed it!!!!
I wondered why a much more superior & powerful machine was having problems, while my outdated P.O.S computer worked flawlessly.
Same story with Connect360 and my Xbox360.
Hard to believe such a little thing having the effect that it did. Thanks for sharing your solution.
I did refer to the thread posted above and did not see that suggestion anywhere, though I only skimmed it. If its missing it might be an idea to add it.
Thanks again and Cheers