Sprint customers who have found themselves unable to contact Google Voice users on Verizon's network. It seems that whenever you try to make a call, it rings once before returning a busy signal -- but the problem goes away when the app is uninstalled. It looks like it's isolated to Sprint users and the people who emailed in are really concerned, since they now use Google Voice for emergency calls. Is there a service outage or something more deliberate? We'll try to find out what's going on, but if you're having the same issue, sound off in the comments, folks.
[Thanks to everyone who sent this in]