NEED HELP CANNOT ACCESS WORKGROUP

Looking for some help here.

I have 4 computers on a fortigate router going out to comcast. LEts just say they are computer A1,A2,A3, and A4.
A1 has a shared file on the computer that everyone accesses and saves information on.
At one point this all worked just fine. Everyone could access, edit and save files to this public1 folder on A1.
A couple people made changes and I do not know what was changed or why, nor can i get a straight answer.

Regardless, i now get "workgroup name is not accessible. You might not have permission to view this network resource...."
when i try to view workgroup computers.

All the workgroup names are correct.
They are all windows xp sp2.
They are in the same subnet.
They all have simple file sharing enabled.
THey all have netbios enabled under tcp/ip settings.
Every computer can ping each other.
I have disabled Mcafee firewall and windows firewalls. Still no fix.
Sharing is setup on A1 for the file to be shared.
HKLM\SYSTEM\CurrentControlSet\Control\Lsa\restrictanonymous is set to 0.


Please HELP!!!!