I've got other crashes when I tried to reproduce this failure.

The logs and rerun.sh are here
http://sqeweb.sfbay.sun.com/nfs/tools/gtee/results/JDK6/ADHOC/VM/2010-02-02_01/vm/solaris-i586/server/mixed/solaris-i586_server_mixed_vm.gc.testlist/ResultDir/jniglobalreflock06

The stack trace is:
;; Using jvm:
"/export/local/common/jdk/baseline/solaris-i586/jre/lib/i386/server/libjvm.so"
#
# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (/tmp/jprt/P1/B/230259.et151817/source/src/share/vm/gc_implementation/g1/g1RemSet.inline.hpp:55), pid=27948, tid=4
# Error: assert((intptr_t)o % MinObjAlignmentInBytes == 0,"not oop aligned")
#
# JRE version: 7.0-b80
# Java VM: Java HotSpot(TM) Server VM (17.0-b08-2010-01-22-230259.et151817.hs17b08-fastdebug mixed mode solaris-x86 )
# If you would like to submit a bug report, please visit:
# http://java.sun.com/webapps/bugreport/crash.jsp
#

--------------- T H R E A D ---------------

Current thread (0x08089800): GCTaskThread [stack: 0x00000000,0x00000000] [id=4]

Stack:
[error occurred during error reporting (printing stack bounds), id 0xe0000000]

Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0x1753b6e];; __1cHVMErrorGreport6MpnMoutputStream__v_+0x5be
V [libjvm.so+0x1754cf6];; __1cHVMErrorOreport_and_die6M_v_+0x586
V [libjvm.so+0x7e5c29];; __1cYreport_assertion_failure6Fpkci1_v_+0x61
V [libjvm.so+0x175464a];; __1cHVMErrorGreport6MpnMoutputStream__v_+0x109a
V [libjvm.so+0x1754cf6];; __1cHVMErrorOreport_and_die6M_v_+0x586
V [libjvm.so+0x7e5c29];; __1cYreport_assertion_failure6Fpkci1_v_+0x61
V [libjvm.so+0x90eb0e];; __1cPHRInto_G1RemSetNpar_write_ref6MpnKHeapRegion_pnDoop_i_v_+0x30a
V [libjvm.so+0x8e763b];; __1cSUpdateRSOopClosureGdo_oop6MpnDoop__v_+0x23
V [libjvm.so+0x56c9a4];; __1cKOopClosureIdo_oop_v6MpnDoop__v_+0x14
V [libjvm.so+0x12e9ff2];; __1cNobjArrayKlassRoop_oop_iterate_v6MnDoop_pnKOopClosure__i_+0x182
V [libjvm.so+0x14e8de5];; __1cPContiguousSpaceLoop_iterate6MpnKOopClosure__v_+0xdd
V [libjvm.so+0x8e6c9b];; __1cbBRebuildRSOutOfRegionClosureMdoHeapRegion6MpnKHeapRegion__b_+0x27
V [libjvm.so+0x8ccdf6];; __1cPG1CollectedHeapbFheap_region_par_iterate_chunked6MpnRHeapRegionClosure_ii_v_+0x192
V [libjvm.so+0x8e6c46];; __1cQParRebuildRSTaskEwork6Mi_v_+0x62
V [libjvm.so+0x1799431];; __1cKGangWorkerEloop6M_v_+0x409
V [libjvm.so+0x1798ec8];; __1cKGangWorkerDrun6M_v_+0x2c
V [libjvm.so+0x132d87f];; java_start+0x117
C [libc.so.1+0xa7045];; _thr_setup+0x4e
C [libc.so.1+0xa7330];; _lwp_start+0x0


--------------- P R O C E S S ---------------

Java Threads: ( => current thread )
  0x09343c00 JavaThread "gc.lock.jniref.jniglobalreflock01.jniglobalreflock01$Worker@a1807c" [_thread_blocked, id=27, stack(0xb4148000,0xb4198000)]
  0x09342000 JavaThread "gc.lock.jniref.jniglobalreflock01.jniglobalreflock01$Worker@1decdec" [_thread_blocked, id=26, stack(0xb4199000,0xb41e9000)]
  0x09340400 JavaThread "gc.lock.jniref.jniglobalreflock01.jniglobalreflock01$Worker@1837697" [_thread_blocked, id=25, stack(0xb41ea000,0xb423a000)]
  0x0933e800 JavaThread "gc.lock.jniref.jniglobalreflock01.jniglobalreflock01$Worker@b166b5" [_thread_blocked, id=24, stack(0xb423b000,0xb428b000)]
  0x0933c800 JavaThread "Locker: nsk.share.gc.lock.CriticalSectionLocker$1@9ed927" daemon [_thread_blocked, id=23, stack(0xb428c000,0xb42dc000)]
  0x0933b000 JavaThread "Locker: nsk.share.gc.lock.CriticalSectionLocker$1@1aaa14a" daemon [_thread_blocked, id=22, stack(0xb42dd000,0xb432d000)]
  0x09337000 JavaThread "Locker: nsk.share.gc.lock.CriticalSectionLocker$1@16a9d42" daemon [_thread_blocked, id=21, stack(0xb432e000,0xb437e000)]
  0x09334000 JavaThread "Locker: nsk.share.gc.lock.CriticalSectionLocker$1@15c7850" daemon [_thread_blocked, id=20, stack(0xb54ad000,0xb54fd000)]
lm153972@vm-x4100-01:/net/sqenfs-1.sfbay/export1/tools/gtee/results/JDK6/ADHOC/VM/2010-02-02_01/vm/solaris-i586/server/mixed/solaris-i586_server_mixed_vm.gc.testlist/ResultDir>
-->c++filt < jniglobalreflock06/hs_err_pid27948.log
;; Using jvm: "/export/local/common/jdk/baseline/solaris-i586/jre/lib/i386/server/libjvm.so"
#
# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (/tmp/jprt/P1/B/230259.et151817/source/src/share/vm/gc_implementation/g1/g1RemSet.inline.hpp:55), pid=27948, tid=4
# Error: assert((intptr_t)o % MinObjAlignmentInBytes == 0,"not oop aligned")
#
# JRE version: 7.0-b80
# Java VM: Java HotSpot(TM) Server VM (17.0-b08-2010-01-22-230259.et151817.hs17b08-fastdebug mixed mode solaris-x86 )
# If you would like to submit a bug report, please visit:
# http://java.sun.com/webapps/bugreport/crash.jsp
#

--------------- T H R E A D ---------------

Current thread (0x08089800): GCTaskThread [stack: 0x00000000,0x00000000] [id=4]

Stack:
[error occurred during error reporting (printing stack bounds), id 0xe0000000]

Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0x1753b6e];; void VMError::report(outputStream*)+0x5be
V [libjvm.so+0x1754cf6];; void VMError::report_and_die()+0x586
V [libjvm.so+0x7e5c29];; void report_assertion_failure(const char*,int,const char*)+0x61
V [libjvm.so+0x175464a];; void VMError::report(outputStream*)+0x109a
V [libjvm.so+0x1754cf6];; void VMError::report_and_die()+0x586
V [libjvm.so+0x7e5c29];; void report_assertion_failure(const char*,int,const char*)+0x61
V [libjvm.so+0x90eb0e];; void HRInto_G1RemSet::par_write_ref(HeapRegion*,oop*,int)+0x30a
V [libjvm.so+0x8e763b];; void UpdateRSOopClosure::do_oop(oop*)+0x23
V [libjvm.so+0x56c9a4];; void OopClosure::do_oop_v(oop*)+0x14
V [libjvm.so+0x12e9ff2];; int objArrayKlass::oop_oop_iterate_v(oop,OopClosure*)+0x182
V [libjvm.so+0x14e8de5];; void ContiguousSpace::oop_iterate(OopClosure*)+0xdd
V [libjvm.so+0x8e6c9b];; bool RebuildRSOutOfRegionClosure::doHeapRegion(HeapRegion*)+0x27
V [libjvm.so+0x8ccdf6];; void G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure*,int,int)+0x192
V [libjvm.so+0x8e6c46];; void ParRebuildRSTask::work(int)+0x62
V [libjvm.so+0x1799431];; void GangWorker::loop()+0x409
V [libjvm.so+0x1798ec8];; void GangWorker::run()+0x2c
V [libjvm.so+0x132d87f];; java_start+0x117
C [libc.so.1+0xa7045];; _thr_setup+0x4e
C [libc.so.1+0xa7330];; _lwp_start+0x0