Computer does not see itself in workgroup computers

Hello

Using Xp Pro Sp1 on my my laptop (ACER) I can connect to the internet
using the gateway provided by the server (DEBORAH) but in the workgroup
(BUGG) the laptop (ACER) does not see itself.

On the server (DEBORAH) I can see the DEBORAH computer but not the laptop
and on the laptop I see nothing at all.

All pings are OK in every direction, on both computers the windows
firewall is disabled and the relevant ports (TCP 139, 445; UDP 137, 138,
445) have been opened, there is no product from Norton on any computer,
all the proper services are up and running (server, workstation and so on)
and I really don't know what the problem might be.

Thanks for the help