Printer prints a line across the paper around three inch from the left hand side of the page.

Duplicated images on pages is either the drum, or fusing/setting unit. Since this is an all in one unit, I am assuming the ink/toner cartridge includes the drum. I suggest replacing the fusing/fixing unit. (the hot part of the printer"

by dragging the black bar on the left with your mouse when
the cursor changes for resize

The flashing light could either indicate a cartridge problem or the printer carrier has stalled.
Test the cartridges one by one and do the printer hardware test (refer to the relevant document for your printer) to establish which one is defective. The defective cartridge needs to be changed. To do the hardware test, follow the steps below:

1. Switch the printer off.
2. Put one sheet of paper into the paper feeder.
3. Press and hold the power button and the paper feed button for three seconds until the power light comes on.
4. Release both buttons. After three seconds, the printer will start to print. You should obtain a page containing a series of horizontal color lines, and a thick black line below these. All the lines should be solid.
5. When the test is complete, switch off the printer. NOTE: If you do not turn off the printer, it will keep on printing this page.

To check if you have a cartridge carrier stall, follow steps below:

1. First unplug the printer.
2. Move the cartridges to the left by hand. In order to do this, you need to grip the top of the carrier belt (a black/grey belt with cog-like teeth) and pull it towards the right-hand side of the printer.
3. Once the cartridges have been moved across, you can clip them out.
4. Try to print without the cartridges in the carrier.
5. If you no longer have a carrier stall, put the cartridges back into the carrier and clip them into place.

Try to print a document to check if printer is working properly now.
If problem continues, please contact Lexmark Technical Support Center for additional assistance.
Sources: - Lights Flashing on the Printer - How to Perform the Hardware Test on the Lexmark X74/X75

Run a half test.
Put paper in the manual feed tray.
Print something, anything
When the paper is 1/2 way into the printer, open the cover.
Pull out the toner cartridge. Look down at the paper.
Does it have a black line on the right side?
If yes, replace the cartridge. If no, replace the fuser.

you may feed a used paper stapled with staple pin and that pin damaged the drum of your printer. now you have to replace the drum

Take the toner cartridge out, shake it back and forth, and turn it around in a circle a few time. Put it back in the priter, and print. Order a new toner cartridge.

If this is an inkjet printer, ignore this response.

Need to Clean the Lance located

could be a fuser problem. interrupt a print and look if the lines are on the page before it enters the fuser (when you still can wipe the toner off the paper).

Does this happen both when copying and printing?
For printing solution, try another toner cartridge.
If lines continue to appear when copying (primarily through the automatic feeder) then lift the auto feeder, and clean the glass -mainly the narrow piece on the left side.

please rate solution :)

the problem exclusive between the drum or the fusser unit