I've been running 12.04 LTS for many months without any problems.

This problem appears to have started after my most recent update.

The symptoms are weird and very specific.

If I boot the machine, I can open any application from the launcher, I can switch between applications, but I can't do anything within the application and I can't close any applications.

In other words, once I've opened an application, that program doesn't seem to recognize the mouse at all.

Also, the bar across the top (sorry, can't remember the name) doesn't see any mouse clicks, so I can't restart or shut down from there.

I can right click on the launcher for an open app, and it gives me the mini menu with "lock to launcher" and "quit", but when I try and mouse over the mini menu, it disappears.

If I just hover over the launcher, the little tag with each app's name will appear.

Infrequently, if I goof around long enough, I can get it to freeze, so the mouse stops moving.

If I power down and reboot, it starts all over the same way.

Any bright ideas on how to resolve this?