All the chips are v 6.0. MIS now sell carts with v6.3. So maybe the firmware update has caused a problem with the older chips. Interestingly enough, I can get all the carts to be accepted individually apart from when I put the black in.
It was running fine with UT14 set in MIS carts until the point at which I swapped in the OEM colour carts and found a couple were running out and then showed as empty. It seemed to accept the MIS carts as I replaced these individually, until the black ran out.
I'm wondering if upgrading the chips would solve the issue, however being in the UK I can't find any local supplies and can't see them on Ink Supply. (plus I doubt whether I could get them by the end of today :-{