I would suggest to just redownload everything. Get the full package and the latest haven.jar and place the latest haven.jar in the main folder. That should work unless somethings wrong elsewhere with java or something.
Edit: by full version I mean the Apoc Lite Update: 2014 19 mar version. Its a zip file with the full client ready to be unpacked and run. If you want to update to the very latest version just replace the Update: 2014 04 may haven.jar. Also run the client using run.bat.