Thought I would reply with my coincidental callout today to troubleshoot an epson workforce 7620. This is a small civil engineer customer of mine (2 employees) who needs wide-format printing. The 7740 is a little bit less than 2 years old, and the symptom was that random lines of a printed page would be "blurry". In fact, it looked clearly like a misinterpretation of what was being printed. it was like the font was severely down-sampled, yet still confined to the height of the line. Bits were missing but you could make out parts of letters in some areas. So on a printed page with 40 or so lines of text, lines 9, 14, 32 and 34 were screwed up, but the rest were perfect. So weird. Same effect in different softwares. Oddly, if you printed a network status page, ever single bit of the printout was bad, but normal word docs or pdfs all had just random lines of garbage.
Customer wanted me to do what I could since the printer was so new. It was installed as a network printer, but the firmware update utility couldn't find the printer (no ability to put in the IP address, just searching). It was also not detected if you connect it by USB - I knew it was toasted then. By logging onto the web interface, I could do the firmware update, but it didn't help the problem. Did an uninstall / reinstall, also a reset to factory defaults & reconfigure. No luck.
In the end, they went out to pick up another printer - the only wide-format one available retail locally was an HP 7740 - hopefully this one will last more than 18 months.