Outlook 2010 and certificate problems

[s-bit]

I have an email certificate from Globalsign which I am trying to use with Outlook 2010. The certificate is on the system successfuly and listed when I attempt to set it up in the Trust Center. However when I go to send an email I get the error: Invalid Certificate Microsoft Outlook cannot sign or encrypt this message because you have no certificates which can be used to send from your e-mail address. - The certificate I am using was specifically created for this email address. Anyone any ideas how to go about fixing this? thanks Simon