After running the megaglest_g3dviewer application, and closing it, I scanned for issues then found this "Open with Application issue : C:\Program Files\Megaglest\m : HKCR\megaglest.g3d\shell\open"
It's always annoying because everytime I open the viewer, nothing's wrong except for not responding after closing when a specific model appears.
I don't see this "m" file anywhere in the Megaglest folder.