I installed the 1.6.3 IDE in the preferred place (C:\ProgramFiles (x86)) and it did not work at all. When I ran it, the splash screen came up, and then it vanished. I reinstalled outside of the Program Files directory tree, and it works fine.
Any chance you can reinstall it in program files x86, start it from the command prompt using arduino_debug.exe and share what gets printed? It may be a bug and therefore we need to solve it