On a PC with two monitors position the secondary monitor to the left of the 
primary monitor and align the bottoms of the monitors.

Start Netbeans on the primary monitor, then drag the Netbeans window to the 
bigger secondary monitor and resize the window to nearly full screen. 
Scrolling now fails.

When scrolling an editor window or a navigator window the system adds new 
lines to the window as it is supposed to, but the rest of the window stays 
unchanged without scrolling. It does not matter wether you cause the scrolling 
with the mouse or the keyboard. If you select part of the unchanged area, the 
correct text will appear.

If you resize the window to a small size, scrolling will be normal.
If you then resize the window to be big, scrolling fails again.
Now drag the window, such that you can see part of it on the primary screen, 
scrolling will now be normal. Drag the window back to the secondary monitor 
and scrolling will stay normal.
If you resize the window to be a little bigger or smaller, scrolling will stay 
normal.

Thus scrolling fails when the Netbeans window is on a secondary monitor and 
you make a big resize of the window. It seems to be due to the secondary 
monitors location (top left corner has negative coordinates). If you move the 
secondary monitor to have positive coordinates, scrolling will be normal.