CompuServe Messages

We are experiencing a print output problem with our LJ 4M. On almost every page printed the print quality at the lower left quadrant of the page is faded or better, text on the page is light or broken up, mainly in the middle of text characters. The rest of the page is perfect. Any ideas whare I should begin to look for a possible solution. We have recently changed toners so have ruled that out as a possibility. The manual does not specifically address this p problem. Thanks in advance.