If the core fails to compile on Dao.DBengine, your system does not have the Microsoft Office 2007 interoperabilty assemblies installed that are needed to compact ACCDB databases. These assemblies are installed with Microsoft Office. You can also download the 'Redistributable Primary Interop Assemblies' from ?this Microsoft web page and install these separately.
This exception indicates a corrupted build environment. Perform Build > Clean solution, close Visual Studio and manually delete any obj and bin folders from the sources folder tree.
A possible cause for this exception is a 64-bit incompatibility problem with the .NET and the Microsoft Access drivers. To overcome this problem, EwE6 must be compiled for 32 bit processors. Set all applications to build for x86 processors via: Menu > Build > Configuration Manager > x86 (new if not listed). See ?image.