3010cn vertical smears all colors

This 3010cn printer has been smearing prints since the day I got it.  If I print simple text then there's no problem.  But, if I print anything like a UPS shipping label with a bar code... anything that uses much toner at all (in any of the colors), then the smears are always there, and always in the same places.  Graphics are completely out of the question.  This has been a problem since it was new, and I've tried to live with it.  I've replaced all the toner cartridges and have tried all the cleaning processes that have ever been suggested.  In cleaning, I've actually never even found anything dirty... including the little sliding bar on the side.  It's still completely white, although I've tried using it many times extensively hoping it would work.  For the purpose of illustrating the problem, I printed out an image at 7.5" wide, centered on a page.  The result is posted for anyone who would kindly take a look and make a comment about what to try next.

http://www.embroidery4u.com/temp/smear.jpg

It would be understandable if the printer had been used a lot and developed this problem over time... but that's not the case since it did this on the very first print I made when it was new and has continued to do so throughout its miserable life.

Any ideas or suggestions would be much appreciated.  Thank you!