Solidworks 2012 SP1. Anyone encountered a negative frequency in the frequency solver? I re-ran the problem varying the input conditions slightly and still receive negative solutions. I am using a spring connector contact set on a frequency problem. Are there known issues with using this type of contact set in a frequency problem?

Sounds like a bug, but I'm not completely sure. Negative eigenvalues are associated with a negative definite or semi-definite matrix; I can't imagine a modeling condition that'd result in a negative definite or semi-definite stiffness (or mass) matrix. Out of curiosity, what was the frequency value that you were given?