Dear Anna: Like your problem is related with the laser unit (ROS ASS), I mean, the printer do not print to the paper the image that have or could have in the drum.
We need to test if this is the problem. To do this, please, with much care: turn on the printer, wait it do it the initial test (5 to 15 seconds more or less), verify have paper in the correct position and the size too in the tray. Print a "config page", but not from "Windows, instead of the same printer. For do this: press Menu, with the vertical or horizontal litle sparrow , chose "print information", then choose "config page" and press the central key to execute it.(See page 32 of this document: http://configpages.blogspot.com/2012/01/dell-3000cn.html)
If you want, look this links beside: ftp://ftp.dell.com/Manuals/all-products/esuprt_printers_main/esuprt_printers/dell-3010cn_User%27s%20Guide_en-us.pdf.
If the config.page was printed well, the printer is not the problem. Try to uninstall the drivers of this printer and then reinstall the right and updated drives from the DELL web link and test again from Windows now.
But if the config. page was printed "in blanking", we have other problem, like the lasser unit.
If you now how to get out a page was have a paper jam in this printer, do it the following actions, if not, do not follow please, because could cause a major problem.
I will give you the actions to take it if you do not resolve the problem with the indicated. Please give your information that what happened.