[Dovecot] Processing too fast?

I'm trying to use Dovecot to make administering ASSP a bit easier. I've created a mailbox with a number of subfolders (Spam, Ham, etc.) and have ASSP setup to save mail in the appropriate folder e.g. /var/mail/ASSP/.INBOX.Ham/new. But I'm having problems with ASSP complaining about the newly created files - I believe the file gets opened, then it disappears before ASSP finishes writing to it.

Is Dovecot grabbing the file from "new" and moving it to "cur" faster than ASSP can write? How can I get around this? ASSP only allows for a folder to save each category to - I can't specify an LDA.

-- Daniel