How Add a COM-Exposed .NET Project to the VB6 (or VBA) References Dialog?
I know this was a long time ago, but I can't find any sensible answers. I had a similar problem and the resolution was to run Visual Studio as the same user who installed it. If I run it as a different user everything except the COM registrations works.
It doesn't give the warning if you run VS2008 under Vista, but not elevated. Elevated is the way we (Vista users) learn to always use the thing, but for this, for some reason, it likes it better the other way.
N.B.: while elevated, mine launched some sort of install for SQL Server Tools that I was eventually able to get past, but when running not elevated, it tries to do this again and fails with permission problems. It doesn't seem to affect the actual build result, though.