[Dovecot] where is subscribed list stored?

[Michael Makuch]

I'm using

$ /usr/sbin/dovecot --version
2.0.15

on

$ cat /etc/fedora-release
Fedora release 14 (Laughlin)

and version 8 of Thunderbird.

I use dovecot locally for internal only access to my email archives, of which I 
have many gigs of email archives. Over time I end up subscribing to a couple 
dozen different IMAP email folders. Problem is that periodically my list of 
subscribed folders get zapped to none, and I have to go and re-subscribe to a 
dozen or two folders again.

Anyone seen this happen? It looks like the list of subscribed folders is here 
~/Mail/.subscriptions and I can see in my daily backup that it reflects what 
appears in TBird. What might be zapping it? I use multiple email clients 
simultaneously on different hosts. (IOW I leave them open) Is this a problem? 
Does dovecot manage that in some way? Or is that my problem? I don't think this 
is the problem since this only occurs like a few times per year. If it were the 
problem I'd expect it to occur much more frequently.

Thanks for any clues
Mike