[Dovecot] corrupted index?

We're seeing the following sporadically in the log file (single line broken into separate lines for readability):

Corrupted index cache file /home/user/mail/.index/.imap/INBOX/dovecot.index.cache: invalid record size

We're running dovecot-1.0.7-2.fc8. The imap directory is in the user's NFS-mounted /home directory, but doveot is running on the same host as the /home filesystem. There's plenty of disk space and no other significant system problems. The mail index directory we rm'd a week/so ago, so doveoct has had the opportunity to rebuild it.

Any ideas on what might be causing this? Is this issue anything to worry about?

thanks.