Electronics in the cartridge interface can be very quirky, as we found out tonight. Ink supply indicators on LCD showed no problem, but printing a page with both black and colored lettering showed black only. I removed and reinserted the color cartridge only to be greeted with the (lockout) message that the Black cartridge (which HAD been printing) was incompatible with the printer. Thinking that the Color I had removed might just have been out of ink, I inserted a brand-new one and got the SAME MESSAGE! I removed it to see if the printer would go to single-cartridge mode (black only) but it WOULD NOT. I then tried removing BOTH cartridges and cycling the machine on and off. I then tried remounting the color cartridge, and this time with just the new Color one it WOULD go into single-cartridge mode and invited me to do the scan alignment. After that, I remounted the black cartridge, did a second scan alignment, and now at long last the 4630 is back to normal.