Outlook 2007 can't edit contact email address

[mbaker-coa]

Hello. I am getting the "Cannot perform the requested operation..." error when trying to double click the contact email address to change the E-Mail properties Internet Format to something other than rich text format. The global mail format setting does not seen to work with some specific contacts, so I am trying to edit the specific contacts that still give AOL user the Winmial.dat file for attachments. Wondering if opening outlook with a /switch will fix this, or run office diagnostics. Other users I am able to edit the E-Mail properties, but one specific user gets the error and won't let me get to the properties box. Exact test or error is "Cannot perform the requested operation. The command selected is not valid for this recipient. An internal support function returned an error." Thanks.