Hi there
I never had that specific problem, but i suspect it is becaue u edited and changed your cloth geometry after applying the cloth plugin onto your polygonal or nurbs object.
A solution might be the leave the geometry but delete all the cloth nodes (write down ur settings!) and then apply the cloth again, that way you will make sure that the geometry has no history that interfers with the computation of the cloth.
not sure if thats gonna help, but i had weird results due to the same mistake 
cheers
thomas