I've been running Flash CS4 (on a mac) for a few weeks now without any major issues. But the last few times I have attempted to import to the stage from Illustrator CS4, Flash freezes up. It allows me to select the file, gives the appearance of loading then the stage remains blank. Menus pull down but all options are grayed out. Any suggestions on how to remedy this?
Have you updated Flash to 10.0.2?
Is the Illustrator file very large/insense number of vectors involved? (ie: if you watch Activity Monitor, does the memory usage grow until things disappear?)
How large/intensive is the FLA you're working on?