Anyone who has got clients on Office 2010 and were updated with the December 9 update may be experiencing issues with workbooks containing ActiveX controls i.e. TI Buttons. As soon as you open the workbook the error is raised and your previous functionality no longer works.
Looks like there may be an official fix for this here.
Good luck.
Please post if this resolves as I do not have anymore clients to test this on.
*Yes, I am asking you to test this for me
