I just append -vm C:\\Program Files\\Java\\jre6\\bin\\javaw.exe
in ec
Whenever you see this error, go to Configuration directory and check for a log file generated just now. It should have proper Exception stacktrace. Mine was a case where I got an updated 32-bit JRE (or JVM) installed which was the default Java that got added to the Path. And my Eclipse installation was 64-bit which meant it needed a 64-bit VM to run its native SWT libraries. So I simply uninstalled the 32-bit JVM and replaced it with a 64-bit JVM.
I wonder if they will improve this reporting mechanism, instead of silently generating a log file in some directory.