Tested the crop as well. Perhaps you are hitting error because the image file that you are uploading is large? Larger images requires more memory and your hosting provider needs to set a higher memory_limit in the php.ini
Could you try to get the error logs from your hosting provider because "Internal Server Error" is a pretty generic error message that could be anything.
However, if this is only related to picture uploads, perhaps PHP isn't compiled with GD. You can check this with your hosting provider