I'm having the same problem with 10.2.1 and 2.7.3. I don't think it's graphics-card related, as I don't have one. (Not a Quartz-Extreme compatible one anyway). So upgrading to Jaguar shouldn't have made any difference if it is the card. It must just be a conflict of some kind. Remember OS9? If you had any 3rd party extensions installed, you more than likely had a conflict. OSX is better, but the problem hasn't been eliminated. Also, have you SEEN the new system folder? It's like a jungle in there, and it could be any two (or more) of the files in there that won't co-operate, or none of them!

I emailed them with the problem, but I just got an automated reply sending me to these forums, 'cause I'm not a 'PRO' user. Let's hope they fix the problem soon.

P.S. The above "diagnosis" is merely speculation, and may well be wrong. It's just my guess as to what's probably the cause, but I'm not an expert on these things by far, so don't rely on it!