Cleaned all the rubber bits with rubbing alcohol. I also went out and bought a Samsung-branded replacement toner cartridge for my nearly-empty cyan toner. Guess what? It physically fits my Xerox printer without any problem but is nonetheless rejected by the printer. Samsung-branded toner costs $50. Xerox-branded toner? $70. Grrr....

EDIT: and I can buy compatible toner for a fraction of that. Any reason for me to buy "original" vs. "compatible" toner?