I had some issues with Slic3r when I tried to open poorly scaled and therefore huge models. If a model is too big by its dimensions Slic3r crashes when adding it. I had this issue with for example this model:
A solution would be to check the bounding box of a model before adding it to the build platform and scaling it down by a specific factor (e.g. 1000) if the units are obviously wrong.
Windows 7 x64
Fit objects to print bed when they are too large and warn user. #2853
That's a great idea. I added a size check that scales the object to fit the print bed and warns user if it is too large.