JRE 6 Update 18 JVM fails in garbage collection intermittently:

hs_err_pid15961.log
-------------------

Stack: [0xfe080000,0xfe100000], sp=0xfe0ffb10, free space=1fefeb61794k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0x761794] oopDesc*PSPromotionManager::copy_to_survivor_space(oopDesc*,bool)+0x68
V [libjvm.so+0x762488] void PSScavenge::copy_and_push_safe_barrier(PSPromotionManager*,__type_0*)+0x74
V [libjvm.so+0x7613c0] void PSPromotionManager::drain_stacks_depth(bool)+0x7e8
V [libjvm.so+0x1c5a60] void CardTableExtension::scavenge_contents_parallel(ObjectStartArray*,MutableSpace*,HeapWord*,PSPromotionManager*,unsigned)+0x7a0
V [libjvm.so+0x1c638c] void OldToYoungRootsTask::do_it(GCTaskManager*,unsigned)+0x38
V [libjvm.so+0x24c29c] void GCTaskThread::run()+0x1d0
V [libjvm.so+0x729768] java_start+0x234

hs_err_pid15982.log
-------------------
Stack: [0xfe080000,0xfe100000],  sp=0xfe0ff9c8,  free space=1fefeb61748k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V  [libjvm.so+0x761748] __1cSPSPromotionManagerWcopy_to_survivor_space6MpnHoopDesc_b_2_+0x1c
V  [libjvm.so+0x762488] __1cKPSScavengebAcopy_and_push_safe_barrier4CpnHoopDesc__6FpnSPSPromotionManager_pTA_v_+0x74
V  [libjvm.so+0x1c61ac] __1cJStealTaskFdo_it6MpnNGCTaskManager_I_v_+0x320
V  [libjvm.so+0x24c29c] __1cMGCTaskThreadDrun6M_v_+0x1d0
V  [libjvm.so+0x729768] java_start+0x234