Quick Start Toolbar disappears on boot.

Each time I reboot I must re-establish my Quick Start toolbar even though I set it and “Lock the Toolbar” each time I re-establish it.
This is something new and ocurred after my system had been running for about a week without shutdown. I’ve checked my toolbar settings before shutting down and Quick Start is properly selected and Locked.
Where is this problem coming from.
I’m running XP Pro with all updates installed (including Office 2003 updates).