I failed to reproduce it on some of the machines I usually use (dumber.east, maple.east, I did over 100 iterations). However, it reproduces every time on the testing box (naboovm.sfbay)
DATE: Fri Dec 19 15:52:13 PST 2008
HOSTNAME: hme0 = naboovm
IP ADDRESS: hme0 = 10.5.20.213
FRAME BUFFER(S): unknown
SunOS RELEASE: 5.10
SWAP: 2638.8MB total, 981.0MB used, 1657.8MB available
LOAD AVERAGE: 1.30, 1.32, 1.30
SOFTWARE SERVER(S): mf-sfbay-04,mf-sfbay-03,mf-sfbay-02
DEFAULT PRINTER: ubur02p20sgl
ETHERNET ADDRESS: 8:0:20:b6:6e:d3
with the latest (as of today, Dec 19, 2008) hotspot-gc. I can reproduce it with debug and fastdebug JVMs, but not with the product JVM (the run would successfully complete). Unfortunately, for some reason, dbx refused to connect to the debug JVM so I couldn't get any more info.
I attached the rerun.sh file from the testing page for your convenience.