On a Mac? If that's the error message you get on a Mac then it's a very misleading error message!
The technology used by actxserver (COM: Component Object Model) is a microsoft design. It is only available on Windows. I know nothing about the IB TWS API but if it requires COM/ActiveX, then it can only be used on Windows.
edit: Just tested on linux and indeed actxserver does return 'invalid progID' instead of telling you that the function simply cannot work on linux/mac. A bit silly really.