Try running 640x240.
288 is 50hz, and 480 is 60hz interlaced...
I've used both a 19 and 25" 7000 with the avga and they both have very good pictures.
Also, are you using a shielded vga cable to go to the jpac?
Is you monitor grounded to the cabinet ground?
How about the computer? Grounded plug to earth ground?
Just a few things to try.
Later,
dabone