The DWG is definitely related to the ActiveConverter.dll running correctly on your system. This tool simply converts DWG to DXF (and vice versa), because in reality ACE 3000 really only works with DXF. You can try any of the following:
1. Uninstall ACE 3000 and then re-install again. Make sure when installing to first Right-Click over the installation executable and select "Run as Admistrator". ActiveConverter.dll is a Windows ActiveX file and needs to be registered on your computer to run.
2. If still problems, make sure ActiveConverter.dll is running correctly. There's not really much more advice I can give you from here because I don't have access to your computer... I would just recommend using regsvr32 (you can perform google search for specific examples of using regsvr32 on 63-bit Windows 7.
3. Use DXF instead of DWG. So when you save from your AutoCAD 2010 simply save as a DXF instead of DWG; and when you export from ACE 3000 select DXF - which can easily be opened by your AutoCAD.
Note: Another suggestion is to make sure that you are exporting DWG formats AutoCAD 2011 and earlier.