Its usually best to raise an iTar for ORA-0600 problems - we've had a number of small issues with memory leaks - usually fixed by putting an event in the init.ora under instruction from support.
You can lookup your ORA-0600 error using
http://metalink.oracle.com/metalink/...&p_id=153788.1
and theres a note on small PGA memory leaks here:
http://metalink.oracle.com/metalink/...T&p_id=39308.1