Where is Photoshop crashing? Have you looked in the Event viewer to see what the specifics of the crash are?
I also use programs that chew up a lot of RAM (VMware as an example) and I don't see Photoshop crash when there's less of it available.
What OS are you running?
Which OS version?
What does the crash report say?
C:\Program Files\Adobe\Adobe Photoshop CS5 (64 Bit)\Photoshop.exe
Event Viewer Report
Ah, the other app is causing problems with your tablet driver, somehow. I doubt that has to do with how much RAM the other app uses.
Which application is causing this? What version?
What tablet are you using? Have you updated the driver?
It was the tablet driver, thanks for the tip