I also have a Linksys BEFSR. I'm nt sure why that would happen. I have my pc setup to obtain the ip address automatically, but I put a static default gateway in the TCP/IP settings (192.168.1.1)
Not sure if I had to or it was just habit.
also with the linksys routers you can usually download an updated firmware for them. Its kind of like updating a ROM bios and it can solve a lot of problems if your current firmware is old.
You can see the date / revision on the "status" page when you web into the router (
http://192.168.1.1)
mine is
Firmware Version: 1.45.6, Jun 24 2003
and I have not problems with it.