Screwy layer visibility

I have mutliple layers in a site i'm designing, and out of necessity (ie my boss wants it, and wont have it any other way) the navigation is based around chaging the visibility of different layers. I forms/fields galore. One of my layers (5) has a number of rows of these fields inserted by a loop. Another 3 of the layers (1, 3 and 4), which are of the same size as the other, also have fields all over them. I also have one text area field which goes from almost the top to almost the bottom of the layer its in.

The probelm is, when i load the page, the upper fields (text, and text box type) seem to act as though they were disable, in that the cursor does not change on mouseover, but the text is still black, not grey as it would be when disbaled. The fields on the bottom of these layers function normally. The top of the text area as this problem, but the bottom doesn't. The exact spot where the problem stops is at the bottom of the lowest field in layer 5. As soon as I make layer 5 visible, then go back to layer 1,3 or 4, all the fields work normally.

I was wondering if anyone has any idea what the  might be going on.