I know you guys are probably getting tired of me and my Samba issues, but I really appreciate you all bearing with me...
First, a couple questions about how Samba stores users... How does this work? It's my understanding that Samba users are stored in the smbpasswd file. However, I've run into a situation where a user exists in that file, but I'm unable to connect to shares with this user nor can I change the password (smbpasswd user) until I first run `smbpasswd -a user`. (This changes nothing in the smbpasswd file, leading me to believe the "allowed users" is kept elsewhere, but I'll be darned if I can find where.) On to the next issue; connecting to shares. Using the newly added smb user, I am able to connect to shares from WINDOWS machines only. If I try to connect to the Samba server using the same username/password credentials in Ubuntu, I get stuck in a loop where it keeps asking for the password and never accepting it. (Ultimately, I cancel and it throws an error about not being able to display the contents.) From this same Ubuntu box, I AM able to connect to shares on WINDOWS machines without a problem. It's only when I try to connect to Samba shares on linux machines does it fail. Can anyone tell me what I might be doing wrong in either situation?

