NP3900 also has firmware problems
At the Streamium Café there is a thread discussing flaws in the latest firmware for the NP2900.
The NP3900 has similar problems. Various ways of using the machine often cause it to freeze, requiring it to be rebooted. Also it often freezes overnight.
The freezing seems to be associated with (1) use of Internet radio; (2) use of network remote controls, and/or (3) night. If I discover a particular sequence of actions which repeatably causes the NP3900 to freeze then I will make a note of it and report it here.