Hi Karina.
I don´t know if it will help you but I´ll share what happened next with me.
I remember I didn´t do anything but updating and rebooting the machine a few times. And it started running well.
After some time though (between opening other heavy apps and working on them) it started again. But a simple OS reboot would fix it.
I´m not shure if it was the speed of my HD for I´m running a good solid pair of top quality HDs on RAID here separated from the OS disc (witch is reliable and fast as well). But then again maybe the heavy use might be an issue.
Thing is I upgraded to CS5 and the same thing happened after leaving the computer on all night and working the whole next day. Only this time it got back on track after the first reboot.
I guess it might have something to do with stressing the OS/hardware but I hope someone else would step up and end all our doubts.
Hope you can get it to work.
Cheers.
adriano