samba - Feb 2007 - File locking: is there some kind of timeout I can alter?

Hi,

I have a problem, that occurs once a week: when my boss opens some files 
with read/write access via vpn over a crappy internet connection and his 
connection gets terminated, some files are still locked read-only after 
several hours/half a day or more. Only restarting the appropriate smbd 
daemon helps.
Is there an option or anything I can modify, that allows me to improve 
this situation?
Reset on vc zero doesn't help, since he might not reconnect everytime 
this happens..
Thnx a lot for any help!

Regards,
Michael