People are/were/still having problems with firmware v1.46
as discussed here (Only 1 bug fixed: v1.46 24/6/04 #1. Fixed DHCP renewal.) Anyway the above link might be useful reading.
I ran with both Cable & Adsl connections on the older version the Befsr41 came with thats why i suggested flashing the router back to an older firmware version.
What firmware version was the router before you flashed it to the newer firmware?