I've installed Office 2003 Pro inWin 8 CP. When I start up a digitally signed Access file I get the usual prompt about the macros and when I view the certificate and choose to Install it I get a new screen that didn't appear before.
Certificate Installation.PNG

I selected local machine then continued. I put it in the Trusted Publishers certificate store and restarted Access. With Macro security set to Medium the macro prompt showed up again. The Trust all content checkbox was greyed out. So I installed the certificate again and let Windows decide where to put the certificate. Restart Access, Trust all content box still greyed out.

These self signed certificates installed just fine in Win XP with Office 2003 and Win 7 with both Office 03, 07 & 10!