As most of you know, ActiveSync has been replaced by a new app called Windows Mobile Device Center (WMDC) on Vista. I occasionally hear from developers who have problems getting their ActiveSync Sync Service Providers (SSPs) to work with WMDC. Usually its a registration issue and the error messages aren't very helpful.
I have a fix that I'd like to share with developers facing such problems. It's a very minor fix and has worked every single time I've suggested it to someone. Here's what you need to do: In the SSP's CLSID InprocServer32 regkey, add a string named "ThreadingModel" with the value "Apartment".
That's it. By doing this, in almost all cases your ActiveSync provider should work just fine with WMDC. Hope this little tip helps any developer struggling with WMDC issues.