[Samba] smbfs locking

[Marcos Pinto]

I have samba 3.0.10 running on a Debian server.  I have other Debian
machines which use smbfs (also 3.0.10) to mount the share.  Every now
and again, the mount will lock and an ls inside it produces an i/o
error.  If i try to umount the share, it gives me a share busy error. 
Now, there is no real i/o error on the server.  I have ten client
machines total which mount shares from the server, and even when one's
locked I can access the information from the others.  The client
machines in use are in a Real Estate company, which needs to keep
certain documents open for sometimes the entire day.  I think that
might be where the problem lies (timeout or some such problem).  As
long as documents dont stay open for hours, this problem doesn't
happen.  Any ideas on what could be going wrong and what I could try? 
Thanks for your help.

Marcos Pinto