I remember reading about another Arrow that broke up within the last few years. The reasons given were that full control movement over stressed the airframe.
Just speculating, but if the weather was poor or IMC around rising ground, its feasible that this recent breakup could have been as a result of over stress due to over control. Ie: disorientation or panic.
Arrows are great aircraft. If there was an inherent structural problem with Arrows, it would be happening all the time as there are so many.