I'd start by doing what bigcountry said and twist or untwist one side of the yoke cable to get it squared up again. I'm not familiar with Martin's strings but some manufacturers have a free floating yoke cable that helps compensate for this sort of thing.

One issue that arises when you twist or untwist yokes is that you'll never get it correct undrawn and drawn. If you get it squared while the bow is at full draw, it won't be square when you let down on the bow, or vise versa.