Hi Boss, are you still interested in resetting the cartridge chip in your C5280??
The following site gives you 5 methods, some of which could be worth a try even though your cartridge isn't actually listed.
http://www.inktec-uk.co.uk/57_58_reset.htm
I think your printer takes the X350.X351,XL350 & XL351 cartridges??
I have just got a new printer which takes the X300/XL300 range and the X300 carts which came with the printer contains only 4 ml. of ink.
As a trial, I have just added another 5 ml of ink to the Black one (and it's working) so that i should at least get double.the printing and I shall keep adding ink to it before it actually runs out or expires just to see what happens.
Just out of interest, my old F380 printer (which has recently failed) used the earlier 21/22 cartridges and I refilled the 21 black cart for over 30 months and it was still printing OK when the old printer failed electrically. It just goes to show how much can be saved if you care to spend half an hour to refill both cartridges every 8 to 10 weeks and it's not as dirty or messy as some people suggest. All it takes is a bit of care and commonsense.
If you are interested I'll let you know how the X300 refill mentioned above turns out???
Cheers,
Wak.