Mixing colors with black: in industrial CMYK four-color printing, it's not uncommon to mix everything in with your black in order to get a darker black. The tradeoff is that if your registration is anything other than absolutely perfect, you get color halos around your letters. Newer printers, both at home and in industry, often use more than the traditional four CMYK colors and have their own proprietary software to do the color separations. You just dump RGB at them and let them sort it out.

Fubar printers: Once you can hook your other printer up, you'll be able to determine whether it's a driver issue, a font issue, etc. Assuming you're billing by the hour, it's likely effective to go buy a brand new printer, just in case, and not even bother debugging the old one.

Cheap-ass printers: I know we've had threads about this before. I've given up entirely on inkjets and now have a Brother all-in-one laser in my office (black & white, duplex, fast, cheap; would be perfect except the Brother software on my Mac insists on asking for A4 scans, no matter how many times I try to switch it to US Letter) and a Samsung color laser at home (also duplex, fast, pricier but will hopefully last a while). The only thing I can't do is make photo prints, and for that I use Costco and their glorious Noritsu photo printer that goes happily up to 12x18". I also have some nice 20x30" prints, mounted, that I did at Fotoflot.