several AWT-related tests threw this during PIT:

# To suppress the following error report, specify this argument
# after -XX: or in .hotspotrc: SuppressErrorAt=\thread.hpp:557
#
# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (C:\temp\jprt\P1\B\235107.et151817\source\src\share\vm\runtime\thread.hpp:557), pid=38424, tid=55364
# Error: assert(thread != 0,"just checking")
#
# JRE version: 6.0_18-b05
# Java VM: Java HotSpot(TM) Server VM (16.0-b13-2009-12-04-235107.et151817.13b-fastdebug mixed mode, sharing windows-x86 )
# An error report file with more information is saved as:
# c:\local\26941.HSX.PIT.VM+windows-i586_server_mixed_nsk.regression.testlist\results\ResultDir\b4261880\hs_err_pid38424.log
#
# If you would like to submit a bug report, please visit:
# http://java.sun.com/webapps/bugreport/crash.jsp
#