Thank you very much.the problem is old enough. happens when the section creates a solid geometry fails to manage (explication to good)
solutions can be disparate, but they assume to understand which part creates error
-move the section axis
-excluding the incriminating part
-move the section axis on another view (sometimes, absurdly, it also works this)
-create a section with a small drying, even a tenth of millimeter (aligned section)
there is also the guide http://help.solidworks.com/2012/ita...kness.htm?id=780b55ce4ee840d0b96f87979a01a2d5