I think the standard fix is to go to
http://updater.pala.de/ and use the Launch button from there to allow reinstallation of the program (use IE or Firefox or any browser other than Chrome, Chrome doesn't handle Java correctly). If it starts from there, reset the desktop shortcuts and if that doesn't clean things up reset all the program settings. If it won't launch off the web site, you may have had Java's autoupdate bork things. Uninstall and manually reinstall Java making sure if you're on 64-bit Windows to install the 64-bit version last if you install it at all, then try going to the updater web site and repeating the above.