verify a far-out MM3 result?

I recently obtained the following enthalpy of formation (298 K) for
 bicyclo[2.1.0]pent-2-ene (C5H6; cyclobutene with a cyclopropane ring
 fused to the edge opposite the double bond):
 MM3	545 kJ/mol	(expt	333 kJ/mol)
 It's so far off I wonder if there's some problem with my copy of MM3
 (came with Tripos' "Alchemy2000" software).  It reports missing
 bond-equivalent parameters for two bonds (the sp2-sp3 bonds)--could
 they be worth -106 kJ/mol each? The corresponding bonds in the
 bicyclopentane are worth +23 kJ/mol each.
 The results look great for these related molecules:
 cyclobutene		MM3 = 158	expt = 157 kJ/mol
 cyclopropane		MM3 = 54	expt = 53
 bicyclo[2.1.0]pentane	MM3 = 156	expt = 158
 I don't think the experimental value is bad:  from G2 I get 320
 kJ/mol and from B3LYP//cc-pVTZ//6-31G* I get 331 kJ/mol.
 I'd be grateful to learn the MM3 result obtained from other software
 (or even from an independent installation of Alchemy2000).
 Thanks for any help!
 Dr. Karl K. Irikura
 National Institute of Standards and Technology
 100 Bureau Drive, Stop 8380
 Gaithersburg, MD  20899-8380
 voice: 301-975-2510	fax: 301-869-4020
 e-mail: karl.irikura