Is .18 the latest version? If not, download and install the latest version of DM. there have been many reports that the calendar in Outlook 2010 doesn't work, especially the 64 bit version.
Use our SEARCH feature to find out more. Lots of posts about it.
In addition to the above, also make sure the default CICAL and default CMIME are both set to an email address, the same email address, and not set to something else like Facebook, or whatever.
In addition to the above, also make sure the default CICAL and default CMIME are both set to an email address, the same email address, and not set to something else like Facebook, or whatever.