I was placing some trees on the edge of the map. It seemed like when I put larger than 1x1 tokens on the edge, and 50% or more of the token was hanging off the map, they would not stay where I put them and instead get stuck in the left most corner of the window, and stay in that position even when I scrolled around. The previous 3 times this happened the token was still highlighted so I was able to undo the move or delete it, but the 4th time it happened, the I must have not seen it right away and deselected the token, so now its stuck there like a phantom that I can see but not select. I left that page and came back to it, and the token is still stuck there.
I'm using Chrome Version 21.0.1180.89 on a Mac running 10.6.8. I haven't yet played the map, so I don't know if it can be seen by players.