Quando avevo il DG814 capitava ogni tanto anche a me'.
Avevo risolto mettendo a zero il timeout , non so' se presente come settaggio sul tuo.

http://kbserver.netgear.com/inquira/...97#__highlight

Routers have a default timeout of 5 minutes, after which the connection is renegociated. There may be a delay, or the connection may drop if there is a problem with the Internet service. The value can be set higher, or to 0, meaning the router never logs out. Consult your manuals for instructions.

Ciao