What is the output of `netstat -in' on both hosts after running
ftp(1)?

This could be symptomatic of having one machine in full-duplex mode
and the other not.  Try explicitly setting both sides to `10baseT' or
both to `10baseT-FDX' (if they're directly connected or you have a
switch).

(There could also be a bug in media selection with the Intel PHY.
Unfortunately, my fxp has a NatSemi PHY, so I can't test that.)