ADO parameter object fails with AS400 when used in Windows XP

I have been using VBA and ADO inside of Excel spreadsheets to upload data
into AS400 tables
for years now within Windows 2000 professional. I am now trying to use
Windows XP and these
same spreadsheets are crashing.

I have tried the following to troubleshoot the problem:
Changing the MDAC version referenced by the program from 2.5 to 2.6 to 2.7
to 2.8
Trying the program under office 2000 and office 2003
Changing the definition of numeric parameter objects from adDecimal to
adNumeeric,
changing the order of parameters objects,
changing the number of parameter objects even just 1.

Under windows XP none of these changes worked but they do work under windows
2000 pro.

I have also dealt with IBM support and they have found through trace files
when executing
the programs that the value being carried by the first parameter object
appears corrupt
whereas the values in the other objects are intact.

Has anyone experienced this problem?
If so have you foound a solution?

I would appreciate any help.

Cheers,
jr2112