Canon i960 grainy prints

I purchased a Canon i960 in January for printing photos. The printer
performed flawlessly and created beautiful prints. However, for about a
month we ran out of ink and had no immediate need for printing. After
that, I purchased some refill inks from MIS to resume printing. The new
prints are extremely grainy and lacking good detail. I'm not sure if this
is due to the new ink, which I doubt since many others have had good luck
with the MIS inks. I'm wondering if it is because the print head sat idle
for an extendend period. I have tried cleaning the head with alchohol and
when doing a test print, everything looks good. The problem only
manifests itself when printing photos.

Any suggestions?

If you have gone through all the Canon Utilities and everything looks
alright then switch back to Canon ink and sees if this clears the problem
after a few prints. Otherwise you probably voided your warranty on the
printer by using non-Canon inks.