Security Update Issues

I’ve seen no side effects of updating my mac (an iBook G4) with today’s security update, but my mom just restarted after updating her mac (a PowerBook G4) and Mail.app marked most of her mail as unread. The fix is simply to create a smart mailbox to show all unread messages and then select all messages in that mailbox and mark them as read. Have any others seen this issue occur? If you have, please comment here. Thanks, genießen, Alex