Hmmmfff. I was under the impression the whole suite was 64-bit.
As I understand it, although all CS5 applications are supported in 64-bit environments, only Photoshop, Premiere Pro, and After Effects are native 64-bit. All others remain 32-bit. (Actually, Premiere Pro and After Effects are exclusively 64-bit -- 32-bit versions are not included.)
Why? I can only guess.
I am wrong and Harron and you are correct only PPro, After Effects Media Encoder and Photoshop and not part of the Suite but Light room is 64 bit and was apparently the first Adobe app that went 64 bit on the Mac.
So when Steve Jobs writes that Adobe is slow to adapt , quote : "For example, although Mac OS X has been shipping for almost 10 years now, Adobe just adopted it fully (Cocoa) two weeks ago when they shipped CS5", he might be right after all!