Have you set your debug level to see if there is anything going on?

Answer the following:
Version of Samba:
How long have you been using it:
Upgrade or changes recently:
Did it always have this problem:
(If not, what changed?)

Have you looked at the man pages for it at Samba -

The following might help but you should check your log files first to try to figure out what is wrong (maybe set the debug level to 3 as recommended by the docs found at their web site)

deadtime (G)
The value of the parameter (a decimal integer) represents the number of minutes of inactivity before a connection is considered dead, and it is disconnected. The deadtime only takes effect if the number of open files is zero.

This is useful to stop a server's resources being exhausted by a large number of inactive connections.

Most clients have an auto-reconnect feature when a connection is broken so in most cases this parameter should be transparent to users.

Using this parameter with a timeout of a few minutes is recommended for most systems.

A deadtime of zero indicates that no auto-disconnection should be performed.

Default: deadtime = 0

Example: deadtime = 15