Same problem in my shop after upgrade to 5.2 and I got so sick of
fighting with it and wading through all the samba stuff on the
internet that I just removed it all and replaced it with IBMs PC Fast
Connect. The PCFC is cheap and supported by IBM.

Back when we were using samba, I was having to reset the samba daemons
every couple of days because they would act all drop connections,
reject conenctions and just act flakey in general. All of the samba
documentation and some forummers I talked to blamed our problems on
the Windows machines which turns out was total bs since PCFC is based
on SMB just like samba and the problems immediatly stopped after
ditched samba for the IBM product.

I was always a little irritated by the fact that we were using samba
for a mission critical function anyway, so it was a very welcome
change. It may be a cliche, but you do get what you pay for.