Hello,

I work on an Excel automation add-in that registers some UDFs and shims to a
..NET and a VB6 addin. Most of the time, this works fine, but sometimes when a
a user saves a workbook, it somehow gets saved in a "corrupted" state, where
on subsequent openings of the workbook, all formulas using our UDFs return
#NAME when Excel triggers calculations. That state then isn't specific to the
machine that the workbook was saved on, if the workbook is sent elsewhere
(for example, to our Tech Support), it has the same problem.

"Changing" any individual formula by clicking into it and hitting return
causes it to "link back up" with our add-in, and it then calculates fine. The
workaround that we have come up with is to tell our users to do a
find/replace through the workbook on "=" with "=", which keeps all formulas
intact and forces them to link back up to our addin.

I haven't been able to find anything in common between the users that are
experiencing it- it is not specific to Office version (we support XP through
2K7), OS version (2K to Vista), or regional settings (Mostly US, UK, but all
over the world). Most of the time, workbooks save fine for these users.

Has anyone seen this issue before with udfs in addins? If not, can you point
me in the right direction to debug / find more information on it?

Thanks a lot,
Thanos