I was trying to enable an add-in for Excel 2007, and I kept getting this error:
Access to the VB project is not trusted
You can turn this message off by going to Developer tab in the ribbon and then clicking on the Macro security button, and checking the check box for “Trust access to the VBA project object model.”
A word of caution: be wary of the add-ins/projects that need VBA access. Don’t allow any project/add-in with VBA access, unless you know its exact purpose or the author of that project.