It seems that the perforce client will not time out requests to the server. So if, for some reason, there is no response the client just sits there. This means that bamboo also just sits there, tying up the threads that could be used for building other things. This is particularly evident when the client and server are a long way apart.

Bamboo needs to have a timeout (preferably configurable) as to how long it waits for the command to return something.