samba - Jan 2013 - failed connect from HP L7680 digital filing

I'm trying to get my HP Office Jet Pro L7680 All-in-one to reliably scan 
to one of my shared folders using the machine's digital filing 
capability.  98 times out of 100, when I try to scan, the AIO 
immediately reports "Cannot connect to \\192.168.254.4\public\scan. Make 
sure the computer is turned on."  The other 2 attempts, it works 
successfully.

My server is currently running Ubuntu Server 12.10 x86 w/ Samba 3.6.6.   
I previously had this working OK on Ubuntu Server 10.04.4 x64 w/ Samba 
3.4.7.  One other notable difference is that 10.04.4 was running on a 
virtual machine while 12.10 is running on a real one.

I'm currently using the smb.conf copied from the VM (see below). With 
default logging, log.192.168.254.5 remains empty.  With log level = 3, I 
get the error "Server exit (failed to receive smb request)"

Not sure what else I can do to diagnose this problem, and would 
appreciate any guidance the community can offer.

----- smb.conf -----

[global]
     workgroup = VIRTUAL
     server string = %h server (Samba, Ubuntu)
     map to guest = Bad User
     obey pam restrictions = Yes
     pam password change = Yes
     passwd program = /usr/bin/passwd %u
     passwd chat = *Enter\snew\s*\spassword:* %n\n 
*Retype\snew\s*\spassword:* %n\n *password\supdated\ssuccessfully* .
     unix password sync = Yes
     syslog = 0
     log file = /var/log/samba/log.%m
     max log size = 1000
     dns proxy = No
     usershare allow guests = Yes
     panic action = /usr/share/samba/panic-action %d

[public]
     comment = Family Share
     path = /media/RAID/home
     force user = root
     force group = root
     read only = No
     guest ok = No
     locking = No

----- log.192.168.254.5: -----

[2013/01/29 13:21:05.865217,  3] lib/access.c:338(allow_access)
   Allowed connection from 192.168.254.5 (192.168.254.5)
[2013/01/29 13:21:05.865449,  3] smbd/oplock.c:922(init_oplocks)
   init_oplocks: initializing messages.
[2013/01/29 13:21:05.865595,  3] 
smbd/oplock_linux.c:226(linux_init_kernel_oplocks)
   Linux kernel oplocks enabled
[2013/01/29 13:21:05.865939,  3] smbd/server_exit.c:181(exit_server_common)
   Server exit (failed to receive smb request)
[2013/01/29 13:21:05.867678,  3] lib/access.c:338(allow_access)
   Allowed connection from 192.168.254.5 (192.168.254.5)
[2013/01/29 13:21:05.867909,  3] smbd/oplock.c:922(init_oplocks)
   init_oplocks: initializing messages.
[2013/01/29 13:21:05.868060,  3] 
smbd/oplock_linux.c:226(linux_init_kernel_oplocks)
   Linux kernel oplocks enabled
[2013/01/29 13:21:05.868392,  3] smbd/server_exit.c:181(exit_server_common)
   Server exit (failed to receive smb request)

Follow up to my earlier request.  Today I created a VM using 12.10 
(Samba 3.6.6).  Both the VM and the real machine are at the same OS 
levle and use the same smb.conf.

If I point the scanner at the virtual server, the success:failure ratio 
was 10:0.
If I point the scanner at the physical server, the success:failure ratio 
was 1:15.

To me it's seeming like smbd isn't waiting long enough--or the printer 
is taking too long, and something is timing out.

Is there a way setting to relax this timing?  What can I do to diagnose 
this further?