Sounds like either the app or one of the individual files might be causing a crash.

1. Try individual files to upload, see if that works.
2. Try a different method of uploading, different app, web browser etc.
3. Open your Eventviewer (eventvwr in the run box) and look in the application and system logs for events around the time the machine crashes, see if you can narrow it down.

There are some good utilities at auslogics.com you can use to clean up your machine and see if that helps.