Fsbuild-2 Flight Planner

So I was flying from MMMX to KORD while I was doing my calculus homework. When I check back after about 10 minutes I see that my flight is now 50 miles off course over the gulf of Mexico. Upon further inspection I come to see that the FMS wanted to fly a leg that was 4000 miles long between two fixes that are less 200. Can anyone tell me what the problem is and how to fix it? See the attatched photo below to see what I'm talking about pay attention to the MFD.

Looks like you might have entered a waypoint in a different hemisphere with the same reference as the one you really wanted. The FMS should offer you the choices available when you enter the reference, with the nearest one at the top of the list, if there are more than one.

Have ran into this on occasion. Generally it is a fix/intersection in a J route that is recognized being half way around the world. Improper coordinate in the navdata I suppose. Always good to step through flight plan before activating.

Right I guess I'll be checking the route before I fly and then correcting NAV Data as the need arises.