Problems with .chm files in Office XP

When clicking on Hyperlinks to explanations in compiled help messages the following error is generated:

! An error has occured in the script on this page.

Line 26
Char 1
Error object expected
Code 0

URL mk:@MSITStore:C:\Program%20Files\Microsoft%
20Office\Office10\1033xlmain10.chm::/html/pphowAlignObjectsOnAGrid.htm

I have run the OFexhelp to replace all of the .chm files and ensured that Office installation is up to date in relation to SPs and Hotfixes but cannot find the root cause of this problem. Help please