dovecot - Oct 2005 - time out error and email with attachments

I'm facing some problem with emails and attachments.
I'm not sure it's dealing with MTU (it is set to the maximum number 
before a fragmentation occurs).

I have no errors from pop3, but the following message is the best I can 
show you just to understand my problem.
The log shows this:

"imap(roberto.cipollini at allmediasolution.com): Oct 04 17:35:03 Error: 
Timeout while waiting for release of exclusive fcntl() lock for index 
file /mail/allmediasolution.com/roberto.cipollini/.INBOX/.imap.index "

I think that the pop3 process is locking the index file (thunderbird was 
  waiting to download the file) and the imap (i tried to get the file 
from webmail) is going time out.

Can anyone tell me how to fix the time out?
any suggestion?
do you need more information/logs?
can I try different setting in dovecot conf?

thanks for any kind of help.
Roberto

Roberto Cipollini <roberto.cipollini at allmediasolution.com> writes:
> "imap(roberto.cipollini at allmediasolution.com): Oct 04 17:35:03
Error:
> Timeout while waiting for release of exclusive fcntl() lock for index 
> file /mail/allmediasolution.com/roberto.cipollini/.INBOX/.imap.index "
I have a similar problem with Dovecot 1.0.alpha3 on a Solaris 9 box.  The
only thing accessing my folders is a single imap process (i.e., the Dovecot
imap binary).  I haven't seen this log message but I do see hangs; gdb
shows this stack trace:

#0  0xff11c32c in _private_fcntl () from /usr/lib/libc.so.1
#1  0xff1162c8 in s_fcntl () from /usr/lib/libc.so.1
#2  0x00038e80 in mbox_lock_fcntl ()
#3  0x00039094 in mbox_update_locking ()

mbox_lock_fcntl gets called inside a while loop; next time it hangs I'll
see whether it's looping or the flock system call is just hanging.
Switching to dotlocking might make the problem go away; flock is supposed
to be faster.

Interestingly I'm the only one of our test users who has the problem. 
I'm
also the only one using Gnus as my IMAP client.