I have only just upgraded to Cs5, on a project I was working on I wanted to use the lighting effect option under filters / render. Has this option been taken away from me to use in Cs5 or is it under another heading?
My mind-reading helmet is a little rusty, but I'll take a crack at your post:
You want the Adobe Photoshop Macintosh forum because you're running Photoshop CS5 in 64 bits. The Lighting Effects filter only works in 32-bits in the Mac version of Photoshop CS5. Check out that forum if you don't know how to run CS5 in 32 bits.