Office 2007 Compatibility Pack issue?

[bradmo]

Setup:
- Managed code UDF, isolated via COM shim
- Office 2003 with Office 2007 Compatibility Pack installed
- Workbook created in Office 2007, uses functions from the UDF assembly

If I save the workbook to .xslx format, close, and re-open it, all of the
UDF worksheet functions are prefixed with the UDF add-in's ProgId and when
calculated the values resolve to #NAME. If I simply click into one of the
cells to get it in edit mode and press return, the ProgId prefix goes away
and a real value is returned.

Why does the 2007 compatibility pack converter add the ProgId to the
worksheet functions and why does using the fully qualified name not work?

Thanks

 

[bradmo]

Correction:
- Workbook created in Office 2007, uses functions from the UDF assembly

Should be:
- Workbook created in Office 2003, uses functions from the UDF assembly