[Samba] Samba doesn't see other computers

[Maurice Kellenaers]

I'm fairly new to linux. I've set up everything and it works, except seeing other computer s in the network.
I can connect with my windows machine to the SMB shares (user) on the linux machine (also with other windows computers)
but I can't see the workgroup and/or it's pc's/servers from the linux machine

I use Fedora Core 3 now (in FC1 everything worked perfect)
in the firewall the ports 137, 138, 139 and 445 are open on TCP and UDP.
In the config I setup my machine and the workgroup correctly
the (hobby wifi) network consists of 7 servers and 53 pc's/clients
The servers run win 2k3 and the clients vary from win95 to xp prof.
My linux machine is server and client

I for myself think I made a simple error (connecting to is working great) but I can't see what I do wrong.
Anyone here with a suggestion?