Hole in pressure plot
 

Strange problem in CFX 5.7.1. I've obtained results for airfoil in subsonic stream and plotted 2D graph (pressure on surface depending on X coordinate). Not bad distribution except little (2-3% of chord) zone, where no line, just a hole. Considering ForceX parameter (affecting on drag) I see great increasing of ForceX in this region. What can it be?