I just recently noticed that not all computers - in fact just a few - are showing up on most computers (Win 7 Pro) including the servers (2008 R2 & 2012). For some reason, they are all showing up intermittently on my computer now though not earlier - not sure what I did other than clean the netbios cache and turn on the 'FDRP' service. Tried doing this on another computer though, and did not have same effect. Network discovery is ON - always has been.
I noticed because I am setting up a new laptop on the domain and it will not retain manually defined mapped drives, and it deletes any network folder icons I put on the desktop after logging off (no sys maintenance going on, I checked).
The only thing I can think of that may have changed is I did a firmware update on my sonicwall firewall last week.
No errors in event logs; no windows firewalls on; network discovery is on the PC's though disabled by default on the servers. I can get to any computer with it's netbios name via '\\servername' in brower or ping servername. Where should I look?