Excel 2010 command button in shared workbook not working

Hello -

I am using Excel 2010. I am using a shared workbook that was originally created in Excel 2003. This workbook has a command button that is supposed to be clicked to open a userform. However, I cannot even click on the button when opening the shared form in Excel 2010. When the form is not shared, the button works fine.

I have no problems with the button when opening the shared form in 2003 or 2007.

Is there anything I can do to make the command button work while the form is shared and while using Excel 2010?

Thank you!