permgen space error

I am using BIRT reporting tool with eclipse but when i try to generate a report it is giving me "permgen space error".

I have already changed the heap size and all possible memory configurations but same error is coming still.

Eclipse Platform Version: 3.4.2
Birt version 2.3.2

Original parameters:
-Xms40m
-Xmx512m
XXMaxPermSize
256M.

Kindly help.