I just learned this one yesterday. Wish I had learned it long ago, as it would have saved me a lot of aggravation. I am assuming this is true for a lot of printers, so I am passing it on.
Being homeschoolers, we use a lot of ink and paper. To save, I have Walgreen's refill my ink cartridges (for an HP 2210) when they run their specials of refills for $5, or I buy the used/refurbished ones at Office Depot or Walmart. Usually they work, sometimes they don't. Or, I will have one that I have used several times and it will suddenly just stop-for no reason.
This happened again this week. My nearest Walgreen or Office Depot is 30 minutes away, so its a real pain to go buy one and bring it home only to find it won't work. And, the 2 I got wouldn't work. I called HP to see if there was a work around as I didn't want to drive all the way back again--I mean we are talking 100 miles for 2 trips.....
I was told to look at my cartridge for a date. There is evidently a microchip in the ink cartridge that tells the printer when that date has arrived. When that date gets here, it is considered to be an expired cartridge and will no longer work. the two ink cartridges I bought were indeed expired (sold to me by Office Depot in October and one had expired in April of 2007). That also explains why ones I have refilled over and over suddenly stop--the date came up.
So, I will no longer refill them close to or past the expiration date, and I will open the box and check the expiration date of refurbished ones at the cash register BEFORE I drive all the way back home.
I thought this was worth passing on!