A rather strange situation

Hi all
 Even though I my Ph. D. thesis work was doing molecular dynamics
 simulations, I don't
 claim to be an expert in the field.  That being said, I have still never
 seen the following
 situation which I will describe to you.  Any input or suggestions will
 be most welcome and
 appreciated.
 I have been doing MD simulations using CHARMM on a small peptide having
 27 amino acid
 residues, both in vacuum and in solution.  I have also done some
 simulations where the peptide
 is heavily glycosylated, again both in solution and in vacuum.
 Originally, the sugars were
 alpha-linked, but now I have linked them beta.  The redone vacuum
 calculation is ok, but the
 solvated system is giving me problems.  By that I mean, when I run the
 dynamics, I get nans (not a
 known quantity, basically) where I would normally get a value.  Yet,
 what I find is strange is that
 the calculation runs, and if you look at the trajectory (i.e., run a
 "movie") everything seems to look
 ok.
 I've tried everything I can think of, including trying to minimize the
 heck out of the system.
 Everything else is the same except the sugars are beta.  My theory (I
 know, bad word...lol) is that it
 has something to do with the conformation of the peptide and the fact
 that it has all these sugars.
 Initially, I had half of the peptide in an alpha-helical like
 conformation (because this was a project
 that someone else had started to work on, and I picked up where they
 left off), and I think that the
 the part that was helical (which has 4 threonine residues, btw, which
 have 9 sugars attached)
 allowed the sugars to interact LESS than they are now.  This increased
 sugar-sugar interaction (?) is somehow driving the energy of the system
 in water through the roof so to speak.  At least,
 that is my theory.
 Does anyone have any experience with situations like this and have a way
 to work around it?  Any additional suggestions are also welcome.
 Thanks,
 Richard
 --
 Richard L. Wood, Ph. D.
 Physical/Computational Chemist
 Post-doctoral Associate
 Department of Food Science
 120 Stocking Hall
 Cornell University, Ithaca, NY 14853