Strange prob with collisions

[tepo]

Gotta strange prob in my network. The server is W2K Adv. with K6-II 450@450 256 Mb with two nic's one to wan, one to lan. Running NAT-routing in it, with NETbios disabled on WAN. (only TCP) On the LAN there is NETBIOS enabled, and that's connected to hub in regular port. Another puter has W2K Prof K6-II 500@500 396 Mb with only on e NIC (of course) with TCP and NETBIOS enabled.
Both machines have static ip's in LAN, I can see everything, almost everything works except:
When I copy files FROM workstation TO server, ( using workstation's explorer) I get horrible amount of collisions in the hub, + the speed is lousy, if I copy files in same direction with SERVER'S explorer this don't occur...???
What a heck is going on ?

Tepo

[DVNT1]

This link may help
http://www.wown.com/j_helmig/speeddif.htm

[tepo]

Thanks, will check it out !