Me (on my gf's iMac G5) and Sebastian (on his new mini) have been experiencing jumpiness that is best described as similair to a caching issue? When you first log on, and afterwards to some extent, everytime you run into something you haven't done yet (dock, asteroid, explosion, etc) is extremely jumpy. It seems to smooth out after playing for a while (hence the reference to caching).

Is this an ATI problem? or ingame?