Are you using ObjectOutputStream and ObjectInputStream
?

This has happened to me many a time and is hard to pinpoint where it
is coming from.

If you are out of stack space and have 128mb of ram  your hardware is
not the problem.

You probable have some kind of infinite loop in your program (check
all of your for loops and while loops to make sure the variable that
is being incremented is actually eventually going to exit the loop.)
this will cause your computer to stack up so many variables that the
stack space (Which I am informed is quite large) will run out.

Perhaps you could download a trial version of JProbe (
http://www.sitraka.com/software/jprobe/ ) and use it to find the
problem.