Samba shares are not accessible anymore in Feisty

[Andis Lazdinsh]

Hello!

I upgraded few days ago 2 computers previously running Ubuntu Edgy to 
Ubuntu Feisty and leave 1 computer with Ubuntu Edgy. Directly after 
upgrading everything was fine with samba shares and they were accessible 
on every computer.
I did only updates provided by Ubuntu official repositories, but 
starting from yesterday I couldn't reach any samba share on Feisty 
computers from other Linux (Edgy and Feisty) machines  without any 
visible reasons. I can access those shared folders from windows xp and I 
can print using shared printers on Feisty machines from Linux and 
windows. All shares are still accessible on Edgy computer. Shares on 
Feisty can't accessed even from those computers, where they are 
physically located.
I didn't install any new program and didn't remove anything. smb.conf 
files looks identical on Feisty and Edgy computers. I tried instructions 
provided in Ubuntu forums to improve smb.conf file, but it didn't help.

I found only mention about /etc/samba/smbusers file which should contain 
user list. I tried to find it, but I don't have it both on Feisty and 
Edgy computers. In spite that authentication of users worked fine until now.

Sincerely,

Andis