I am almost to give up by finding a solution on some client machines (Windows 7, Firefox 41, IE 10).
The problem: one Java Web Start application sometimes does not start from browser: a splash screen appears saying Java Starting... and then nothing happens! It does not even try to check/download the resource files, or write into java cache, no entries are found in the Windows Event Log.
I have tried:
- Reinstall JRE (8u73)
- Clear java cache (via control panel)
- Clear browser's cache
- Enable tracing and logging (nothing is written then)
- Reduce the heap size to 512M
- deployment.trace.level=all(still nothing is written)
- -Djava.net.preferIPv4Stack=true(no affect)
- JPI_PLUGIN2_DEBUG=1,- JPI_PLUGIN2_VERBOSE=1(no affect)
- jstack browser-pid(attach is not possible not HotSpot VM!?)
Even without applying any changes, after some waiting, sometimes the application does start from the browser!?!?
Following behavior is observed: a javaws process starts and then disappears, sometimes(rarely) following error message is thrown: c++ runtime error ...jp2launcher.exe... can not be started...R6016 - not enough space for thread data
BUT it always works if started per javaws.exe http://...xyz.jnlp command!?!? 
