LG Flatron 795FT Plus - horizontal lines on screen

I've got a LG Flatron 795FT Plus computer monitor which is giving horizontal flickering lines obscuring the lower two-thirds of the screen.

here's an image showing the problem (not very clearly though - click on it to get it bigger):

http://img440.imageshack.us/img440/9749/dsc00237ls2.th.jpg

occasionally, it clears up and everything is ok, but then the lines come back again later. what's going on? do i need to buy a new monitor, is there some setting a can change on the monitor, or is there a quick, easy repair possible?

(i've done a few basic tests and determined that the video card is ok, seems to be a monitor issue only.)

any help appreciated, thx!