Strangely enough two other, apparently knowledable persons, have almost the same problem. Do you by any chance have the same distro ?
either there must be problem with login, or the mount fails for some reason (what happens if you mount to a new mountpoint, not through "mount" or "smbmount" but by just adding a line to fstab ?
The differing servers probably dont matter.
(man smbmount v3.0.20b):
One smbfs bug is important enough to mention here, even if it is a bit
Mounts sometimes stop working. This is usually caused by smbmount
terminating. Since smbfs needs smbmount to reconnect when the server
disconnects, the mount will eventually go dead. An umount/mount nor-
mally fixes this. At least 2 ways to trigger this bug are known.
three people, why not each of you make the following: with konqueror
first browse /mnt until you get no further
then browse smb:// (servers_IP_number) until you get no further
and smb:// ( workgroup ) until you get no further
compare your results, and you may at least learn where the problem lies.