Today the Windows Update Service at the office offered me XP SP3 (as a developer, I have the privilege to choose which update to install). I knew about no issue about the tool I use, and decided to install it.
When I rebooted, the quick launch bar and address bar were gone! Ok, let's re-enable them, I thought. The quick launch bar was simply disabled - but the "Address bar" item in the tool bars menu was gone!