BLACK SMUDGING MY PRINTER GIVES A BLACK SMEAR ON THE FRONT EDGE OF PRINTING DOWN THE CENTRE FADING BEFORE HALF A PAGE?

Hmm... This sounds like it is a toner problem. If your roller is getting too much toner then it just globs it onto the paper even though the drum is not asking for it. Are you using a new toner cartridge or a re-filled one? Is it from Brother or a 3rd party? I suggest you remove the toner cartridge and check inside the printer. Clean any spilled toner. Check the toner cartridge for leaks .. give it a good shake and see if it is leaking. If you have another toner cartridge, you can replace it to test. You may need to pint a few pages to see a change. Another test could be to print a few (2-5) "BLANK" pages. The printer should not be depositing any toner. If no smudge or the smudge stays the same, then the toner cartridge is the likely problem. If the smudge is there, but gets smaller, then clean your printer.

Good luck!