This build requires a 64-bit JVM, and will not run with a 32-bit JVM.
You can, for example, use the Sun 64-bit 1.5 JVM for AMD64.  Note
that the Sun 1.4.2 JVM for AMD64 is 32-bit and therefore cannot be
used to run this build.

The Eclipse 3.3 - 3.6 launchers for Windows have a problem with the Oracle/Sun Java VM version '1.6.0_21'. You have two choices to work around this:

1. switch back to '1.6.0_20'
2. add the following line after "-vmargs" to your eclipse.ini:
-XX:MaxPermSize=256m

See https://bugs.eclipse.org/bugs/show_bug.cgi?id=319514 for more details.