Hi Nunu
It is unclear which PI version you are on. This will determine which NWDS version you should use and the corresponding JDK.
Troubleshooting PI ESR and Integration Builder Logon Issues - Process Integration - SCN Wiki
Check the "Supported Java Web Start Versions" section in the above link. It states which JVM the different PI is running on, you should then use the corresponding JDK.
Ex: PI 7.3x runs on JVM 6.1 --> use JDK 1.6 (also called JDK SE 6 - latest version is 6.0_45.)
Note that PI 7.4 requirement is not listed there, but it is same as 7.3x.
Rgds
Eng Swee