Frequently when teleporting, the teleport progress screen goes blank with the only visible thing being the progress meter, which just continually fills up until you eventually get logged out from Second Life. What appears to be happening here is a miscommunication between Sim A (origin) and Sim B (destination). Sim A receives a "false positive" for you having connected successfully to Sim B, when in fact the connection had failed, or had "almost" succeeded. So, when the TP fails, you are stuck in limbo, rather than simply reappearing back at Sim A, since you are no longer connected to Sim A. This is based on an observation I made yesterday evening while I had been logged in with two viewers running simultaneously. I TPed home with my alt, but the teleport failed and the alt was booted. Before that happened, the teleport progress screen went from saying "Requesting connection", and then went blank. The moment it went blank, my alt vanished from where he was standing in-world, which normally does not happen until the connection is completed and you are en route to your destination. To fix this behavior, I suggest being more conservative with how Sim A would drop a client's connection. IE: It needs to be certain that the client is connected. The best way to go about this is to make Sim B tell Sim A to close the connection after the client has been connected fully.