I think my switch is not capable of converting from thinnet to ethernet. I installed another networkcard in a winxp pc. The win xp pc was as well unable to get an ip and I had limited or no connectivity to internet. So the hub is not good. I will do some more testing this weekend by hooking up the debian and the winxp to each other (give them both an ip) and ssh or transfer some files over samba orso.
Btw the hub is a 3com as wel (TP4combo "Office connect").