I have multiple versions of Java installed, both Sun JDK & JRockit, both 32 bit and 64-bit, etc. and ran into this problem with a fresh install of 64-bit Eclipse for Java EE (JUNO).
64-bit trio as suggested by Peter Rader:
I'm using 64-bit Eclipse on 64-bit OS (Windows 7).
I ensured Sun JDK 7 64-bit was the default java version. When I typed "java -version" from command line (cmd.exe), Sun JDK 7 64-bit was returned...
java version "1.7.0"
Java(TM) SE Runtime Environment (build 1.7.0-b147)
Java HotSpot(TM) 64-Bit Server VM (build 21.0-b17, mixed mode)
This did not resolve the problem for me.
Adding -vm option to eclipse.ini as suggested by Jayesh Kavathiya:
I added the following to eclipse.ini:
-vm
C:/apps/java/jdk7-64bit/bin/javaw.exe
I did not have to uninstall any of the various versions of JDK or JRE I have on my machine.