COPY THE AREA ON SIDE. HATCH IT. THEN COPY HATCH AT ORIGINAL PLACE. SEND IT BACK IF YOU WANT TO SEE THE CONTENTS. DELETE TEMPORARILY COPIED BOUNDARY.
Sounds like you might have a case of polylines "looking" closed but not actually "being" closed!
If a polyline only looks closed then the first and last points will be the same. If a polyline is actually closed it will have been drawn by clicking the penultimate point then pressing "C" or "Close" to close it.
Use the properties box to tell which your polyline is. The Closed field is under the "MIsc" section.
dJE
Under properties check if the selected Pline is closed. Right click on the hatch and select Set Boundary. Do not erase the linework. This will reset your hatch to your PLine. This is also a good way of updating hatched areas if the hatches are not set to be Associative.
Hatches can be troublesome at times. Good luck!
Easiest way to 'fix' this, is to type 'BOUNDARY' command. Pick a point within the area you intend to solid fill and recreate the boundary of that area. Move the created boundary to one-side and you will be able to solid hatch this for some reason! Not really a fix but an easy get around.
L