Menu bar locked in app!

While using any app in OSX 10.6.8, the menu bar (at top of screen) will suddenly lock in that app. For example, the menu bar will be stuck on Safari, only displaying safari and its menu commands. When i click on Mail, or any other app, already running or not, nothing happens.

The keyboard will only allow typing in the app the menu bar is stuck on. The dock and desktop become unresponsive and won't allow me to close/open apps, to log out, or do a shut down or restart command. The system doesn't allow a force quit of any app, and none appear in the "Force Quit" command list from the Apple menu button. My only option is to physically turn off and restart the computer.

Using the "Repair Disk" utlility does NOT solve the problem.

This problem happens nearly every time I use my mac, sometimes multiple times in a day!