(EDIT: The jar file on the server has now changed...)
It's hard to help without any background, code etc.
Given that the jar file itself is invalid (I've just downloaded it and tried to open it) I suspect you did something like uploading it to your hosting provider in ASCII instead of BINARY mode.
If my psychic debugging powers have failed this time (and this was really stretching them) I strongly suggest you give us more information - importantly:
- How did you build your jar file?
- Does your jar file work locally?
- How have you uploaded it to your hosting provider?
Looking at the jar file with a hex editor, it appears to have some Java source code in it in plain text - uncompressed which would be somewhat odd in a jar file. It also doesn't open as a valid zip file...