Originally Posted by Fishheadjoe
Best guess, check the nut hight on the G string... might be cut too low.
Once the note is fretted, the nut is no longer part of the equation.
How would a, "too low nut", affect the frets?
"open G is fine "--Not the nut, then.
Try raising the G string saddle, to begin with. It sounds as though the OP may have made a radical string change, in which case having the bass setup would be called for.