CMS: assert(thisOop->is_oop_or_null(true),"expected an oop or NULL")

http://vmsqe.sfbay/nightly/mantis/DTWS/results/04-18-06/ClientVM/Solsparc/mixed/Gc_Baseline-Xconc/RT_PLUMHALL-19-NIGHTLY-Gc_Baseline-Xconc-ClientVM-mixed-Solsparc-2006-04-19-04-13-05/hs_err_pid25365.log

shows an assertion failure

    # Error: assert(thisOop->is_oop_or_null(true),"expected an oop or NULL")

with this stack trace:

    Stack: [0xfae00000,0xfae80000), sp=0xfae7f4b8, free space=509k
    Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
    V [libjvm.so+0xcfc084];; void VMError::report_and_die()+0x7f8
    V [libjvm.so+0x3b2f70];; void report_assertion_failure(const char*,int,const char*)+0x70
    V [libjvm.so+0x37c5e0];; void PushOrMarkClosure::do_oop(oop*)+0x84
    V [libjvm.so+0x393490];; int constantPoolKlass::oop_oop_iterate(oop,OopClosure*)+0x2a0
    V [libjvm.so+0x76e7c];; int Klass::oop_oop_iterate_v(oop,OopClosure*)+0x60
    V [libjvm.so+0x3799f8];; void MarkFromRootsClosure::scanOopsInOop(HeapWord*)+0xb78
    V [libjvm.so+0x378c80];; void MarkFromRootsClosure::do_bit(unsigned)+0x614
    V [libjvm.so+0xe7f9c];; void BitMap::iterate(BitMapClosure*,unsigned,unsigned)+0xec
    V [libjvm.so+0x365488];; bool CMSCollector::do_marking_st(bool)+0x24c
    V [libjvm.so+0x3611f4];; bool CMSCollector::markFromRoots(bool)+0x1c4
    V [libjvm.so+0x35b278];; void CMSCollector::collect_in_background(bool)+0xcc0
    V [libjvm.so+0x388d3c];; void ConcurrentMarkSweepThread::run()+0x814
    V [libjvm.so+0xa870e0];; java_start+0x17c