Random Layer void problem. Probably something simple

Hello everyone,

First of all I would like to apologize if this has been answered before. I honestly dont even know what to search for answers.

I have been having a serious problem with Corel painter 12. This is now my second artpiece that has been ruined after about 10 hours of painting.

I normally have 4 layers that are stacked as follows:

-A second lineart with added affects such as burns.
-Details with soft oil pastel and airbrush
-Color fill with soft oil pastel
-Basic lineart layer

Simply put, when I am painting I get to a part of my drawing where it does not let me paint over. It acts as a void and won't let me place anything inside it. Erasing doesn't work, nor effects, different brushes, or anything. I call it a "hole" in my paper because thats the only way to describe it.

The strange part is, I try the same thing on every layer and it will not let me paint or erase that hole. On one of my art pieces I can color in the hole, but it does not help because I have to switch back and forth between two layers. On the other piece, I tried filling the hole on every single layer and nothing will add color inside it.

New layers created, even if they are placed on the foremost ground of my painting, can't be painted on.

I am losing hope and would gratefully appreciate some advice from people more experienced than I am.