Problems with dovecot (imap server)

[Jd <jd_(_at_)_jackdan_(_dot_)_net>]

Hi, I have a mail server running postfix + dovecot (acting as imap 
server).  Since my ISP blocks port 25 in and out, I use fetchmail to 
bring the emails to my server. 

I have only 3 email accounts running.  2 of them seem to run flawlessly, 
but the third one is really starting to act weird.  Some emails seem to 
duplicate themselves (10-15 copies of the same email sometimes).  For 
exemple, I would print out all the emails in the morning.  30 minutes 
later, in 1 shot, I get 60 'new' emails, which are actually copies of 
the emails I had printed out before.  This only happens on the account 
where we get the most emails (around 150-200 a day); some of the email 
directory (mbox type files) have over 60 megs/4000 emails. 

Has anyone ever had problems with dovecot and large email volumes?  Like 
I said previously, the 2 other accounts have absolutely no problems, but 
are also muh smaller in size (MB and emails).

System is running: 3.4-RELEASE (src and ports) + dovecot 0.99.10.5 
(emails are in mbox format)

Thanks,

JD