Windows 2003 storage server network problem

Strange problem with Windows 2003 storage server, which is a member server
in a native 2003 AD domain.

Can't connect to the 2003 server(not even with ping to IP-adr.) from any
other computer (linux/WinPC's/SunSolaris)
before the connection is initialized from the 2003 server with for instance
a ping to a remote computer.
The arp cache on the 2003 server then get updated with the remote computer,
and everything is OK(Connect to Win shares/NFS shares etc.) until arp tables
times out on the 2003 server. Again no connection is possible, not even with
a ping to IP-adr.

The 2003 server can connect to any computer internal/external if initialized
from it.

A Cisco router can always ping the 2003 server sucessfully using
name/IP-adr.

The 2003 server is listed in DNS/AD, with a PTR in the reversed zone and the
lookup works and is correct from remote computers pint of view..
The IP-address on the 2003 server is static(no DHCP)

Same subnetwork, no firewalls involved.

Everything was fine until a couple of days ago, no changes to switches,
cables has been done. (no other changes as well that i can recall)

All other 2003 servers(std. edition) works fine and are using the same DNS
server as the 2003 Storage server

I guess this is a routing issue, but i cant put the finger on anything
specific. Anyone got a clue whats wrong?