I upgraded from Photoshop CS3 to CS4 and am having issues with photoshop crashes attempting to use Magnetic lasso. The lasso is not outlining selected object, no visible lock box or line and Photoshop ceases to respond. I am working on an iMac 10.5.6, 2.33 GHz intel core 3 dua, 3GB Ram and a Nividia GeForce 7600GT 256 MB VRAM. 

When photoshop locks some of the items in the dock have changed to lines of color or at another point the outline of the image I was working on remained on screen. I have run permissions and check the disk and all is well there.

I am presently involved in scanning over 1,000 images and restoring them. This, coupled with not having a method to import directly into CS4 from my scanner, has disappointed me with CS4. Especially having used Photoshop 7 for years in a Windows environment, having purchased CS3 when I moved to iMac a year and half ago. 

I considered resetting my VRAM but did that for the first time in the last month. Not sure what the issue is but sure don't have much time to be troubleshooting.