SQUAT failed to open index file, SQUAT failed

[redhatdude at bellsouth.net]

Hello
I sent this email before but I got a reply about it being spam. So if  
you got it twice, please excuse me.
Anyway, here is my problem.

I'm running Postfix with cyrus-imapd and squirrelmail together. In  
the postfix log I'm starting to get this message quite often:

SQUAT failed to open index file
SQUAT failed

What exactly does that mean and how can I fix it?
Thanks
EJ