>When I try to select the VB 6 API Viewer from the Add-In Manager I get the error message "The API viewer was loaded but could not be added to the menu. Unload the add-in through the add-in manager dialog, choose view blah, blah, blah...." I've tried unloading it as they suggest but no luck. I'm able to load other add-ins with no problem.

Have you seen this one: http://www.levelextreme.com/wconnect/wc.dll?UniversalThread~2,33,Forum=21,29,755