Does an employers breach of contract invalidate a non-compete?

I previously worked for an insurance agency and signed a non-solicitation agreement at the start of my employment. I have since left this agency and started my own agency. My non-solicitation agreement prohibits me from working with their clients as well as prospective clients that we solicited business from. I have a very specialized expertise that nobody at my previous agency has and prospect a very specific type of client. My previous agency is using deals that I had begun negotiating before I left the agency to solicit some of my previous prospects even though they do not have the expertise to handle the account. The reason I left the agency was financial. They paid me a small salary (about 1/5th of what I was making at my previous job) and then agreed, in writing, to pay me commissions based on my sales. They paid me my salary but never paid one penny of commissions I earned. This went on for nearly 3 years before I left. I requested commission payments several times and was told I would be paid but never was. A few weeks after I quit they finally paid me my commissions. I believe they were in breach of contract by not paying me. It made it financially impossible to stay with them and now I am afraid they will try to enforce the non-solicitation agreement if I try to work with former prospects. What are your thoughts? Thanks!