>>>Is it possible that the MTU value was changed during the router installation?<<<
Nice thought, but the test at
http://www.dslreports.com/tweaks says MSS requested=1460 (default ?)
It recommended an RWIN of 7300 which I set with Dr TCP, but still getting between 57 kbits/sec and 65 kbits/sec. Also tried a fresh install of win98se with all its default settings and got the same results

Trying another NIC next . .