i need help every time i try to convert the polygonal object that i want to make a Cloth object it gives me a error and the object just vanishes. the error is as fallows

Error: Invalid geometry. Solution may be unpredictable.

i dont understand why im getting this error. can anyone give me a possible reason why? ther then what its stating and how i could of come to this point.

as you can see im trying to convert some pants i made out of Polygons into cloth. and yes the pants do have more then one side. as it has pockets....

i was wondering could that be the problem?