I have a model USR8000-02 NAT Router/Firewall. I use it for dial-up. I noticed that it was bombing out after connection, or required frequent resets. This was intermittent at first, but then as a year went by, it got worse and worse to the point where it didn't work again.
I went to the website and downloaded the firmware upgrade for 2.7. I already had 2.7 firmware, but I did it all over again.
Voila! Problem solved. It now needs no resets (yet) and stays connected without bombing right after connection. It is also much snappier, to my delight! I imagine over time I'll need to redo the firmware upgrade again, however, but at least with that small chore it will keep this thing connected and running okay.
You might want to keep that in mind if you're having trouble with yours.