after a couple of hours of frustration with my mac and the eternal question:

why wont java use more than 2GB of RAM, if the system has 8GB Ram I found the answer here:

http://developer.apple.com/java/javaleopard.html

basically you need to provide the JVM flag -d64

thanks apple for doing something simple so complicated. On every other os java automatically uses 64bit without the need to set some stupid flags...