Here's a strange one: I have 2 Xerox 6280s bought at the same time. One of them seems to be going through ink roughly 4x faster than the other. Taking the black ink cart out of the working 6280 where it read 'low' and putting it in the 6280 in question- it sees it as empty. Put back in the first 6280 and it once again reads as 'low'.