Got some problem with EP curve and isoparms
 

Hello i am rather new to 3D modeling so i would be thankfull for any help i can get with my problem maybe another solution.

I am modeling a helmet like head for a robot i am making but i have got a problem with the isoparms.

The helmet is made out of a nurbs sphere and i am using EP curve and project to cut out the geometry, where i want to make a hole in the sphere.
But when i am trying to select the isoparm, where the edges of the hole is, I cant select the isoparm.
But i am able to select the isoparms on the rest of the helmet.

I have submited some screenshots maybe you can understand what i am saying better by looking at them.

I have created a EP curve on a NURBS sphere.
Then selected Project curve on surface.
I then use Trim tool to select what geometry I want to keep.
I then select isoparm, but when I try to select the isoparm, where I cut the geometry with the EP curve nothing happens all the other isoparms are selectable.



Like i said i would be very thankfull for any help i get.