Since upgrading to 12.04, I've randomly experienced this strange phenomenon where my mouse mostly doesn't work and keyboard mostly does. I have not been able to identify a cause for this. Sometimes it will happen minutes after I start-up, other times after the computer has been idle for a while, and other times in the middle of working on something. It lasts until I reboot the computer or restart Gnome.
The mouse won't be able to interact with any open windows, but if I do ALT+Tab, I can't keyboard nav through those, I can only click to change windows that way. Same if I press the Windows key; the keyboard remains focused in whatever window was just active but I can click things with my mouse to open new programs.
Anyone else experienced this? What might be causing it? Is there a fix?