> Yup, the default pass rule on LAN lets fragmented packets through.  I
> also reflashed the offending NSLU2 to see if dodgy firmware was to
> blame.  Now I'm left wondering if a bad network cable could be the
> problem, as nothing else has solved it.


Having changed over the network cable it hasn't made a difference. 
Also, I've installed Ubuntu Linux over the previous Win2k installation
on my desktop at the 192.168.0.0/24 network which now stops me from
connecting to any work machine over SSH.  Previously, I could connect
using PuTTY.
Trying "ssh computeratwork.workinternaldomain" lets me accept or deny
the key for the work host and then asks me for the password.  Checking
/var/log/auth.log on that machine shows that I enter the password ok
and then the ssh connection just hangs - the m0n0wall logs then show
packets being blocked on port 22 as before.
I can connect via SSH to the WAN address of the router at work (i.e.
not using the VPN) fine - my home m0n0 just blocks some packets, but
not all, from crossing the VPN.
Any suggestions would be welcome as I'm completely stumped.

Tim