It’s odd that it occurs randomly like that. From what I’ve seen on Creative Cow and Adobe’s forum, the solution you found is what should correct the problem.
Maybe the last resort is to uninstall and reinstall AE?
Like you said, I’m not sure if there are any issues with the new video card you installed. How much RAM do you have allocated to AE in the preferences? Maybe try increasing that, or enable disk cache?
Stay away from iMacs if you’re looking to do anything beyond hobby work. You’re basically just buying a computer that limits you. Where as something like the Mac Pro is very easily expandable. Or save yourself a ton of money and get a PC .
Very true. The new iMacs are quite capable for certain things – and would likely offer a good speed increase versus the laptop you’re currently working on – but if you plan on doing a lot of intensive rendering (as it sounds you are), the iMac probably isn’t the best course to take. As Mark mentioned above, they are extremely limiting in terms of expandability and customization.
Of all the research I’ve done, the best bang for the buck is the 6-core 3.33GHz Mac Pro. Sure, it’ll cost you a pretty penny, but you’ll be blown away by the performance.
Just don’t cross over to the dark side by getting a PC!