You may have a bad chip. If you have a set of cleaning cartridges, snap out the cartridge from the bulk system that is lit and put in that same color cartridge from the cleaning set. If the light goes out then you know the problem is the chip on the bulk system cartridge and replace it.
Like Harry said if you have another cartidge of the same color (each one is location specific) then try it to test but sometimes you can remove that cartridge and clean the gold contacts on it and replace and that might fix it. I have found keeping a spare set of cartriges on hand is a good investment, even though my replacement carts have the auto reset chips I have also had them just quit working completly. And ink flow problems can also often be helped with new carts.
Hope this helps
Kip
If no cartridge or cartridge chip change solves your problem you can look at the "prongs" or connectors inside of the carriage. They are the small wire looking things that make contact with the chip on the cartridge. They are spring loaded and can get stuck or not spring back into place to make contact with the chip. You can gently pull them back into place if you see some stuck. I use what looks like a dental pick to do this. Just be gentle you do not want to break the contact or wire off. Inspect them and make sure that they are all there. It is possible that over time that a cartridge "grab" the prong connector and break it off. Also check for any ink that may be on them preventing a good connection. If you do have to clean ink from any of them DO NOT get any liquid on top of the printhead that may get into the head cable connection. That would be a disaster.
T-jet 2, one ink light doesn't turn off!!! 
