Unfortunately I'm not able to attach the original excel files, maybe sometime in the future, but I was able to find the source of the error.
One of the lines in the excel data exploded one of the equations to infinity. I was able to rewrite the equation to avoid this. It' strange that this exception came up, but I think it must be memory related.
It was quite hard to track down the error because it didn't highlight the particular equation, only the whole set of equations.
Thanks.