I'm able to reproduce this on Oneiric. Steps to reproduce:
1. Open a fullscreen RDP session using remmina on top-right workspace.
2. Switch to top-left workspace.
3. Select Remmina from Unity launcher. This will switch to the top-right workspace.
4. Focus Remmina by clicking anywhere.
5. Use CTRL-ALT-left arrow to switch back to top-left workspace. Tooltip for Remmina on the launcher should now be stuck.
I'm able to reproduce this on Oneiric. Steps to reproduce:
1. Open a fullscreen RDP session using remmina on top-right workspace.
2. Switch to top-left workspace.
3. Select Remmina from Unity launcher. This will switch to the top-right workspace.
4. Focus Remmina by clicking anywhere.
5. Use CTRL-ALT-left arrow to switch back to top-left workspace. Tooltip for Remmina on the launcher should now be stuck.