Excel 2010 - Windows 7 64bit.

We received a spreadsheet from a client. This spreadsheet has a macro button in it that generates an email based on the filled out form.
It works perfectly for myself and several other users. However, for the group of users that need it, the macro button does nothing. I click it, and it generates an email properly. They click it, and nothing happens at all.

I went thru and compared their security settings in the trust center with my own, and we match up perfectly. None of us are admins on the machines and for the more part, our machines are identical in terms of software and patches.

Does anyone have any suggestions as to what might be blocking it for them? What other security could there be? The can work around it by logging into citrix where it DOES work for them.

Any thoughts?