Transition States Exercises - 3rd Year Computational Lab

Introduction

On a potential energy surface, a minimum is a point at which

Diels Alder

So done the IRC - looks like its been successful - got to check about the optimisation of th eproducts at the PM6 level. I have optimised it and got a negative frequency of -44 but when using the Hartree-Fock 3-21G method I got all positive frequencies. Is this wrong?