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?