ActiveX Command Button Not Working On Some Computers When Workbook Is Shared

I am updating a shared Excel project and have come upon a minor issue. ActiveX controls (or at least Command Buttons) won't work on one machine when the workbook is shared.

The machine in question is running 32-bit Windows XP and 32-bit Office 2010. The project has been tested on another system that matches these specs and everything worked fine, but on this one particular machine, the button becomes unclickable. It isn't disabled, at least not by appearance, but nothing registers when it is clicked.

I've tried fiddling with the ActiveX options in the Trust Center but nothing there made any difference and, as I said, it works just fine on other computers with the same version of Office and Windows XP.

I could switch the ActiveX Command Buttons to Form Control Command Buttons and it would work fine but they've grown used to the different colored buttons they've been using for years and would prefer to keep them if at all possible.

Has anyone come across something like this before? If so, are there any solutions?

Forms controls are more reliable.