Vill bara bekräfta Andreas information.
Workarounden som beskrivs i hans länk fungerar, men det är inget kul att fippla i Kontrollpanelen om man inte vet vad man gör.
Det gäller alltså JRE 7 update 51 där man infört denna säkerhetsförändring:
"Starting with Java 7 Update 51, Java has enhanced security model to make user system less vulnerable to the external exploits. The new version of Java does not allow users to run the applications that are not signed (Unsigned), Self signed (not signed by trusted authority) and the applications that are missing permission attributes."