The open- and saveAs-dialogs can crash in the DWG preview generation, when the AutoCAD file AcSignCore16.dll is installed on the computer. This file is obsolete and it can be removed or renamed. The file can be found in the folder:
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​C:\Program Files (x86)\Common Files\Autodesk Shared

and in the folder:
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C:\Program Files\Common Files\Autodesk Shared