I just got this:
Sorting mailbox...*** glibc detected *** double free or corruption (!prev):
0x08131658 ***
AbortedI did "quit"/"yes" while there was 1 deleted message in the ! mailbox. So this may not be specific to pop/imap "fetchmail" handling. -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]

