> [...] 
> at various times, the network locks up and I get errors like:
> 
> traceroute: sendto: No buffer space available
> 
> which persists until I do "ifconfig ep0 down; ifconfig ep0 up".
> 
> any ideas what could be causing this, and how to fix it?

me too! :-/

I thougth it's a problem w/ my network (cabeling isn't up to date
here, and those silly N[in]T[endo] and Windooze 3.11 peecee's are 
sometimes having really noisy conversations w/ the netware box...)

The system in question is a Toshiba XCDT480 w/ a 3C589Combo card
running -current. hm, the ss5 (-current, too) on my desc doesn't have
any (network) problems... and a bunch of old 486's running some 1.4++
are also ok...

not much help I think, but....

    -kurt