Disappearing menu bar and minimize button quits working

Question

I'm working in Entourage or Firefox (with about 3 other small applications open and Classic is running) and the screen suddenly blacks out, as if a screen saver came on for about a quarter second, then the screen comes back. The Menu bar is gone. I can get the menu bar back by clicking on the background and then clicking back on the application, but the minimize button no longer works on the open applications' windows. If I open a new application, the minimize button works on that window. Sometimes I have trouble getting the menu bar back, depending on the application that was open when it "blinked". When this is happening, it occurs at about 20 to 30 minute intervals. Any ideas of what's happening? Has anyone experienced something similar?
Power Mac G4 (AGP graphics)   Mac OS X (10.4.8)   400 MHz, 512 MB RAM

Answer 1

You can check that you do not run Firefox in full screen mode (Mac: command+Shift+F).
*https://support.mozilla.org/kb/how-to-use-full-screen
See also:
*http://kb.mozillazine.org/Corrupt_localstore.rdf
You can also try to remove the Firefox plist file (org.mozilla.firefox.plist).
* http://www.macfixit.com/article.php?story=20060606082246983 How .plist files become corrupt and troubleshooting the results
Go to "~/Library/Preferences" and remove the plist file for Firefox (org.mozilla.firefox.plist)