[Dovecot] Mailbox locking problem with iphone and POP3

I have a problem I can't seem to fix. I have dovecot configured to do 

POP3 with plain text authentication using a MySQL database. I am using Dovecot 1.0.7 with fcntl locking.

My problem has been when an iPhone/iPod checks email. The iPhone/iPod 

doesn't disconnect with a TCP FIN packet and it leaves the mailbox in a locked state and prevents the user's desktop from checking email. I have tried changing the file locking method and other config file options without any luck.

Oddly, I am using the last version of cucipop on another server with 

fcntl and lockf file locking and it doesn't have this problem.

If someone could clue me in I'd be very grateful.

Bill