hi Arkroyal
The cartridges in question are chipped and this chip on detecting a low level sends a signal to prevent the printer operating. As you say sometimes this happens with lots of ink still remaining. There is a commercial chip resetter available which will reset the chip and allow the printer to function again. I have posted a link where you can purchase this item. It is probably only worth it though if you intend to refill the cartridge yourself when it eventually does fully empty.
Regards
Willby
http://www.inkjetcartridges.com/epso...r-CREPSON.html