I provide hosted telephony and my preferred router WAS the VR400.  My broadband supplier requires me to provide a VLAN of 101 for connectivity.  When installing the routers things connect and the router works perfectly.  The problem comes in that every now and then the router will lose its VLAN ID and disconnect.  When the VLAN is entered again the router connects and works well until it loses the connection again. The time periods are completely random.  I have now had a situation with a router that lost its VLAN ID and whatever I do it simply keeps dropping the connection and not connecting at all.

I do like the routers in general but cant continue supporting 50 routers with this problem and its driving me up the wall.  Has anyone had this situation in the past and managed to find a confirmed solution?  

All firmware it up to date etc.