Unable to connect to network, but I can connect to websites, FTP, etc

My network is setup like this:

+Router
-XP Computer (named vaio)
-Debian Computer (running samba, named dell)
-X-Box running X-Box Media Center

All are in the HOME workgroup and there is no domain.

I am able to see/use the debian machine's samba files through the XBMC interface and
it shows up when I browse the network, but not the XP computer. I did used to be
able to (as of a week ago) but something has changed and I'm not sure what.

When I browse my network (Home) through My Network Places>Entire Network>Microsoft
Windows Network>Home, nothing shows up (not even my own computer).

Computer Browser and TCP/IP NetBIOS helper services are enabled (but ipconfig /all shows netbios over tcp/ip as being disabled), Windows firewall is disabled and the names(dell/vaio/Home) are correct and haven't changed. Any ideas on what I need to do to fix this?

Check your firewall setting and make sure that the File annd Printer Sharing is allowed. If it isn't in you firewall to allow them you can add them manually.

TCP ports 139 and 445
UDP ports 137 and 138

Hopefully this helps

Are you able to ping each computer?

What happens, for instance, if you go to the XP computer, open up a run prompt and type "\\dell"? or \\vaio? You can also do this in a web browser.