I had a strange thing today, and figured I'd let y'all know about it...
I suddenly lost the internet connection, and, after a little poking around, realized the Internet indicator on the router and the Ethernet indicator on the DSL modem were out. It was like someone had pulled the cable between them. At first I thought maybe the indicator was out because the PPPoE connection was gone, but I compared it to another router and found the indicators are the standard link lights, and shouldn't go out.
After some messing around, I did a hard reset on the router and the connection came back. I re-entered my setup information and now it's working fine.
I have two BEFSX41 set up nearly identically, one at each end of the VPN tunnel, but only one had this problem. I'm using the new 1.52.9 firmware, which has been very good so far.