[Samba] Clients periodically disconnecting

[Chris St. Pierre]

Samba 3.0.21c, RHEL4.

About a week ago, we restarted our Samba server because nmbd had run
amok.  Since that restart, our Apple clients have periodically
disconnected -- by most reports, they disconnect every 15-45 minutes.
It doesn't appear to be synchronized, i.e., every Mac on campus
doesn't disconnect at once, but only occasionally.  They get a message
similar to:

"A server you are using is no longer available.  Do you want to
continue trying to contact it?"

(This varies by exact OS revision, of course.)

Our Windows clients do not exhibit this behavior.

I turned up the logging for a few users for whom this was reliably
happening.  The following are the last few messages before it
disconnects:

[2007/02/13 10:08:57, 3] smbd/sec_ctx.c:set_sec_ctx(288)
   setting sec ctx (0, 0) - sec_ctx_stack_ndx = 0
[2007/02/13 10:08:57, 5] auth/auth_util.c:debug_nt_user_token(433)
   NT user token: (NULL)
[2007/02/13 10:08:57, 5] auth/auth_util.c:debug_unix_user_token(454)
   UNIX token of user 0
   Primary group is 0 and contains 0 supplementary groups
[2007/02/13 10:08:57, 5] smbd/uid.c:change_to_root_user(324)
   change_to_root_user: now uid=(0,0) gid=(0,0)
[2007/02/13 10:08:57, 5] lib/username.c:Get_Pwnam_alloc(290)
   Finding user jrandom
[2007/02/13 10:08:57, 5] lib/username.c:Get_Pwnam_internals(234)
   Trying _Get_Pwnam(), username as lowercase is jrandom
[2007/02/13 10:08:57, 5] lib/username.c:Get_Pwnam_internals(267)
   Get_Pwnam_internals did find user [jrandom]!

Any ideas?

Chris St. Pierre
Unix Systems Administrator
Nebraska Wesleyan University