Don't know if anyone else has come across the problem but I have found
that the 660-jre extracted from the tar archive doesn't quite work.
When setting ide properties for example, on selecting the Colors&Fonts
tab the console displays a message
java execl cannot create robot....
or words to that effect and idea hangs.
The remaining java processes have to be kill -9 for them to die.
Changing the startup script to use my existing jdk1.4.1 seems to work ok.