Subtle and peculiar network hardware problem

[steve at horne.homelinux.net]

I recently bought a laptop on ebay (long irrelevant story) which
has a problem I've neber seen before.  When I set up the built-in ethernet,
everything seems to go fine.  Works in Knoppix (first time), and in xp (after n reboots, for large n -- maybe a clue?)  

"seems" is the key word.  I can ping out, dns lookups work,
at least in knoppix.  (I think pings worked in xp too.)


But I can't use ssh, or a browser.  Even in knoppix.

When I plug a network card into the pcmcia slot, the pcmcia
card works fine in all respects in both knoppix and xp.

I have used these laptops before (kds, that's wy I bought it) with no
problems.

The question -- is it possible that the hardware is somehow broken,
so that pings work, and dns lookups work, but 
nothing else???

The alternative explanation - that neither knoppix nor xp has an adequate 
driver - is hard to swallow.  The factory software was just reinstalled from
the recovery disk. 

The interface is identified as  Realtek RTL8193, if that helps -- 


                           Thanks,
                                 Steve