I agree. ActiveX controls can be problematic, especially between versions.
If there are other alternatives, I'd recommend using them. In addition to
Stephen's calendar, which is API based, and Allen's calendar, based on a
form. There is a form based calendar which has been working (with
conversion, as necessary) in every version of Access beginning with Access
2.0 and continuing through the Access 2010 beta:
http://www.datastrat.com/Download/Calendar2K.zip
There are also several calendars at the Access Web.