We have an HP Laserjet 1160 that is putting a wrinkle down the middle of the page from top to bottom on every page it prints. The wrikle is about 1/8 to 1/4 inch wide and normally has a thin black line running through the middle of it. We have swapped the toner with another 1160 and still have the problem in the original printer. We have also changed paper to make sure that is not the issue. Any ideas?