Why is my 2155cn black ink printing extremely light/barely perceptible?

I have a 2155cn that is still under warranty for another 145 days.  For the last few weeks I have been trying to figure out why my black ink is barely showing up on the paper.  In the beginning, it was visible, but more of a gray color that black.  I thought that maybe the option to "Print Black as Color" was selected when I initially received the call, however, that was not the case.  Since this began, we have ordered a new Dell branded toner for replacement and the problem is still here, if not worse.  Now we can barely read the text at all on the paper.  I am attaching a scan that I did of a sample of a full page of text.  The sample has some color highlights to prove that there is text on the paper.  I have no issues with color printing at all.

I am not having any luck resolving the issue or figuring out who I should call regarding this problem.  I hate to spend any more money on toner or other parts if it will still be unusable in the end.  The printer identifies a full black toner installed and no errors are given on the display.  I have tried different drivers (PCL 6 and XPS) for Win 7 x64 thinking that might help.  Still have the same problem.  I have tried looking through the printer menu, but I am no printer expert, so I don't want to pretend to know something I don't.  Any help would be greatly appreciated.

If you need any other information, I'll do my best to get it to you.

Thanks,

Chris