crashes, random logouts

Since a few days I'm experiencing multiple crashes. Some programs crash almost immediately after opening. For example, every time I open an image in Photoshop, it crashes.

The error message is always the same:
Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0x00000000f08b2b51
Crashed Thread: 0 Dispatch queue: com.apple.main-thread

Another problem: from time to time my MacBook logs out all users without any warning.


I have a MacBook 5,1 with 2x 4GB RAM (which has worked fine for me for months). I tried to work with 4GB only (I tried both), but the same problem remains.


Does anyone have an idea what it could be?

Thanks!