We expose an interface to our simulation software using a COM/ActiveX object. This worked just fine in XP, but in Vista, we get "Error 429: ActiveX can't create object" when a VB client executes CreateObject().

The COM object has been registered by hand so that the Vista Registry is identical to XP's Registry. I run the VB interface from a DOS window that I started using "Run As Administrator". The client is correctly accessing and reading the Registry as I walk through using the debugger in VB, so it's apparently not a security setting, as near as I can tell.

I have also loaded the files into VS2005 (the object was originally created in VS6) and rebuilt them to get a later ATL version, but that hasn't helped - we still get the 429 error.

Is this a symptom of UAC problems, or should I be looking for something deeper?