First check the printing settings you use when you send the work, especially the quality (low quality prints fast, but has smaller dpi than high quality). I'd also check whether the settings guide the printer to use black or color for printing; I've met some cases where color was used to print "black", which was more like grey or blue than true black.
Edit: if it's not the settings, then it's very probably the driver you're using. Check that the driver you are using is meant for that exact printer model you use, and that it has been tested to work (e.g., is not commented as "works somehow" or equivalent), if you downloaded it from somewhere.
Last edited by b0uncer; 07-19-2011 at 04:21 AM.