My 17" flat panel G4 iMac monitor has has lost its luminosity latitude. There are no visible gradations of color. Regular photo images are mostly black with only the brightest parts of the image visible. Illustrator files don't show gradients. Any color that is not 100% fades to white. Calibration doesn't help. Does the monitor need replaced? Is it normal to replace a 2 year old monitor? Can it be repaired?