Problem with Theme Editor

Hi,

I have installed Ep 6.0 SP12 along with KM. I want to customize it, but when I open the theme editor in the portal, it shows portal runtime exception and the stack trace in the logviewer shows "JAVA.lang.outofmemoryerror".

I upgraded my heapsize to 1.5 GB using config tool.

but i get the same problem.

any sort of help is appreciated

Thank you