perl_alloc or perl_clone?

I've finally moved to Perl 5.8.7 (ActiveState) for my
Java application that uses perlembed (using JPerl as
a JNI wrapper).

With Perl 5.6 we got sporadic crashes, but it seems
the threading support in 5.8 is ready for prime-time,
so I removed the mutex synchronizing all the Perl calls
and the crashes are much less frequent, but alas,
the app still crashes maybe once every 20,000 perl calls
or so:

Unexpected Signal : 11 occurred at PC=0xE6BBDF60
Function=[Unknown. Nearest: Perl_savesvpv+0x70]
Library=/export/home0/brennan/dev/mainline/lib/JPerl/solaris/libjperl.so

I'm wondering if switching to perl_clone() instead
of perl_alloc() would help.  I haven't totally narrowed
it down yet, but it's crashing in one of these 3 routines:

perl_alloc()
perl_construct()
perl_parse()

Apache modperl2 uses perl_clone().  Doesn't seem there
is much advantage to it, and it probably calls perl_alloc()
under the covers anyway.

I've googled and read the perlemb and perlthrtut, but I'm
not sure what to try next.

Any suggestions?
Thanks,
JD