Autocad 2015 file Preview in Windows 7

I just upgraded from Autocad 2014 to Autocad 2015. Every .dwg file I open and save with Autocad 2015 loses its thumbnail preview in windows 7.

Thumbnail preview settings are checked in Options, THUMBSAVE is set to 1, and I have tried the popular solutions from the Autodesk Support Forums (installed DWG Trueview, made sure PreviewVisible is set to 1 in the REGISRTY EDITOR), but no joy.

I realize the thumbnail preview is not a major component of working with Autocad, but for large drawing folders the preview makes finding the correct drawing much faster.

As a note, the .dwg files are still set to save in a AutoCad 2013 drawing format (as was the case with Autocad 2014), so I don't know why upgrading to 2015 would have caused this issue with windows 7.

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