I can help you with this. Can you open photoshop and then open activity monitor. Next to the photoshop process in the list you see it says intel, if it says intel(64 bit), it's running in 64bit mode.
I checked the activity monitor. Next to Photoshop in the list it does say Intel, but it does not have (64 bit) after Intel. Many of the other items in the list say (64 bit) after Intel. For example, Safari shows up as Intel (64 bit).
Ok, we can change this. Control click on the application. Then, select get info. In get info you will see a check next to open in 32bit mode. Uncheck this and photoshop will running in 64bit mode.
Ok, I did what you asked but there was nothing there saying open in 32 bit mode. I can send you a screen capture if there is a way to attached it to this document. Also my problem with CS5 saying I am out of RAM occurred in CS4 and on another computer as well as this one. I keep thinking there must be a corrupted file somewhere.