What does SMB connection failed mean, and is there anyway to debug this?

I am using *identical* mount -t smbfs commands on 4 computers: 2 redhat 9.0, 1 suse 9.1, 1 fedora core 1. It always works on the redhat computers (thank goodness), never on fc1, worked a couple times on suse and then stopped. I've also tried /etc/fstab/ and I keep getting the error:

SMB connection failed

With /etc/fstab that's all I'd get back. With I'd get a message like:
28264: Connection to WINPC failed
SMB connection failed

or 19602: Connection to WINPC failed
It's never the same 5-digit number.

I don't think it's a firewall issue because I've checked on firewall on WINPC, and it's open. Also, strangely enough, from Konqueror in KDE on the suse laptop, I can see smb://WINPC/Main Drive/ as a share and browse it. But when I try to use Konqueror to mount, it also tells me that it failed.

What can I do to figure this out?

For suse,

/etc/samba/smbfstab

//BOX/C /mnt/C smbfs username=administrator,password=whatever,uid=joebob,gid=users,rw