If you can ping around without errors or packet loss then your network is fine.
If you have double checked to make sure that NetBIOS over TCP/IP is enabled on all adapters,
click start orb
type
ncpa.cpl
hit enter
select then right click the adapter and choose properties
uncheck IPv6
select IPv4 and click properties button
click the advanced button
select the WINS tab
select the radio button that says
Enable NetBIOS over TCP/IP
OK your way back out of there.
If all of that is correct then you, as I said earlier, need to uninstall any and all third party Internet Security Suites (Symantec/Norton, McAfee, AVG, whatever) and all third party software firewalls (Comodo, ZoneAlarm, etc.,) using the add and remove programs applet...