I picked up a second hand IBM Model M "clicky" keyboard (series 52G9658) and connected it to the PS/2 port of the "HP Z400 Workstation" here at work (this model M variant has an integral PS/2 cable.) I'm running Ubuntu 10.04 with the latest updates and Gnome 2.30.2.
$ uname -a Linux tp-dev-01 2.6.32-31-generic-pae #61-Ubuntu SMP Fri Apr 8 20:00:13 UTC 2011 i686 GNU/Linux
Whenever I hold down shift and use the arrow keys to select some text on the screen (either in a web form, in gedit, in Eclipse, anywhere) and then press either the delete or backspace keys, I can't click with the mouse anymore! Attempting to select any menu items fails; clicking in another text box (attempting to click in Chrome's address bar for example) doesn't work, alt-tab doesn't work.
Fortunately, if I click on apps in the "task bar" (or whatever Gnome calls it) making my VMWare virtual machine active, then click around in a Windows instance for a bit and then click back to Gnome, everything goes back to normal.
Does anyone have any idea how this could possibly be happening and what I can do to fix it?