Closing Workbook in Office 2007

Hi,

I am testing a number of add-ins that currently work without issue in
Excel 2000 running on Windows 2000
(The add-in has its code module secured with a password)

When I run the call the same add-in from XL 2007 running on XP
professional it also works without issue.

However on closing the workbook the user is faced with a request to
enter a password for the vba project

Any thoughts would be much appreciated

Points that may be relevent:
I removed and reapplied the security within Excel 2007 to no avail
The add-ins still have add/remove button code that Office 2007
converts to a ribbon item

Cheers

Kieran