Cannot Access server Via \\name only by IP

Something happened in my network the other day ( not sure what yet) but
now I cannot see one of my servers by name unless the workstation is
joined to the domain?

My old situation was.
2 Servers ( Both Win 2003 , AD, DNS, DHCP )
I have multiple shares set up on one server (MAIN) and also some shared
printers
My users also have shares and printers set up that were mapped using
the server name
\\main\contracts or \\main\HP_Color_Printer

Now since what ever it was has happend, I can no longer communicate
with the MAIN server using the name \\MAIN To connect I have to
either use \\192.168.0.251 or \\main.metrolaser.local

The only acception to this is if the particular workstation is a member
of the domain, then \\main works fine. The problem here is that we have
various outside contractors that we do not wish to join to our domain
but would still like them to have acces to certain shares and printers.

One last observation is that when I log into the MAIN server and I
browse network places and the into our domain it seems that MAIN is the
only member of the Domain as were if I log into any other workstation
on the network (server or client) I see all computers in the list that
are a member of the Metrolaser domain????

Sory for the long post, I am at a loss here, I'm no DNS guru but I
think everything is setup OK... Any suggestions?

J