Artifacts in menu (get white/not select)

I don't know where post this, but I'm getting since yesterday a weird behavior in OS X Snow Leopard.

I don't know if is related to XCode/iPhone SDK or what. Sometimes, with no apparent reason, the menu of the application become FULL white. Then in the emulator I get distortions in controls (the edit not show characters when input, but the control are getting it).

Also I lost the Command-Z in the xcode editor. Other glitches are around but I don't remember it right now.

I have a white macbook MacBook2,1.

 

Also I found that I have no Command-Z because the Edit menu dissapear! (The top "Edit" is in the menu but no single sub-menu exist).