Desktop becomes half highlighted in orange after using workspace switcher.

After using the workspace switcher in the unity dashboard in 11.10 a few times - a strange orange highlighted box covers half the screen vertically, on the left hand side. It disappears and reappears intermittently. What seems to trigger it is when I mouse over the left edge of the screen to pop the unity panel out of hiding. It lingers till I use the workspace switcher to open a different panel which doesn't show it, but returns once I mouse over the unity panel again. It's really annoying. While the highlighted box appears my cpu fan begins to run. I checked the system monitor and see compiz is using 25% of my cpu resources while the bug is present. And nothing while isn't.

Thanks for your time.