Hi
I have searched on the Microsoft website for some solution proposals and found this:
Unable to Browse the Network" When You Click Network Neighborhood
http://support.microsoft.com/kb/260214
This behavior can occur if there is an AutoLogon key in the registry at the following location:
HKEY_Local_Machine\Software\Microsoft\Windows\CurrentVersion\Network\Real Mode Net
It seems you can solve this issue by deleting the AutoLogon value from the registry location listed in the "Cause" section.
Check also this:
Network Error (1222): Unable to Browse the Network
http://support.microsoft.com/kb/170336
Good luck