Pen works but quits working randomly in Photoshop CS4

I just installed the Genius MousePen and it keeps repeating this behavior in Photoshop CS4: it works perfect in Brush mode until I hit Ctrl-Del to clear the desktop (and sometimes other commands as well). Then it starts drawing really faint straight lines, regardless of pressure. I've tried everything to get it back to the regular Brush mode, and it does eventually go back but I can't seem to figure out why it starts and stops like that.

Any help would be greatly appreciated.