Volume disappears ?

Hey guys..

I have a strange problem.

Sometimes when creating a mill volume path , it can´t be mill because the mill volume suddently disappears.

I´ve had this problem a couple of times , but not every time.

I make the seq , choose the volume (which appears in solid) , and everything seems okay. But when i try to play the path , the volume is gone.

You can still see it in the modeltree , but not select it on the model..

In this case i´ve fix it with a mill vindow , but still real frustrated..

Have anyone had similar problems ?