I may have a clue (or it could be a red herring) for this one, Kristin C. I see this problem not often, but not infrequently either. Maybe 1 time in 5, something like that. It pans out like this...
1. I assign control of a token to "Player A" and tell him, "go for it".
2. He says, "that's funny, I can't select the token".
3. I then also assign control of the token to "Everyone" and tell him, "try now".
4. He says, "okay, thanks, that's fine now".
5. Without telling him I then remove the "Everyone" control and leave it just as controlled by "Player A".
6. It continue to work fine.
If nothing else, it's a potential workaround for you, Blake G.