HP Officejet 7310xi

Up until one hour ago I was happy with this printer/scanner/fax which I bought at Costco. When I printed a simple document, half the lines were missing! After several printer cleanings, which use up paper and expensive ink, the printer is almost printing normal again. I had an Epson that would not print well after weeks of non-use, but I expected more from this HP printer. If it keeps giving me trouble I'll have to take advantage of Costco's return policy (you can return anything except computers anytime for any reason).