COM class factory for component error

[u156531]

I know this is a very generic looking error but I'm hoping someone can give me an idea of what casues this and where to start looking for the problem. Stage Two Retrieving the COM class factory for component with CLSID {9AAF0EB6-42D8-46C1-A2EF-679511B37A0D} failed due to the following error: 80040154 Class not registered (Exception from HRESULT: 0x80040154 (REGDB_E_CLASSNOTREG))

Thanks, Mark