I was going from Fanfoot Flare to Elyssian Slope and fumbled on the keyboard as I selected the new street to go to. The "which thing do you want to interact with" popup appeared, and remained on the screen as the new street was loading:
skitch.com/dopiaza/r5sah/sc...
Once the new screen loaded, the popup was still there:
skitch.com/dopiaza/r5sa4/ga...
I clicked on the map, and the popup disappeared.
FF 4.0, OS X 10.6.7