For some reason Office 2003 Professional decided to stop working and started demanding the install CDs (under my XP Home Fusion setup). It kept moaning about requiring the SKU111.cab file.
A MS web page covering the error I got says it could be for a variety of reasons:
http://support.microsoft.com/kb/896866
Anybody else suffered from this under Fusion?
Note the fix mentioned at the bottom -- downloading and using the Local Installation Source tool to copy across the CAB files so that if it happens again you won't need the install CD.