My 4400 had a blocked yellow nozzle, so I tried a regular clean, followed by 3 power cleans (at great cost in ink grrr...). No change, so I found a "supersonic clean", care of Vicky at Conde on Youtube. Tried that, now 6 of the 8 heads are blocked. Great. I've tried everything I can think of since, including:

Regular Cleans
Powercleans
KK0, KK1, KK2 and KK3 cleans
Soaking paper towel in water, Mr Muscle, Isopropanol and leaving it under the print head for various periods of time from 10 mins up to 36 hours
Filling spare cartridges with isopropanol and running power cleans to flush the system through completely
Pushing ink and/or isopropanol through the tubes with a syringe
Using a kit from Printheadhospital.co.uk
Phoning Epson (who won't touch it as it has Artainium ink in)
Praying to various non-existent deities.

Anyone got any other suggestions before I put it on ebay for parts? (apart from DON'T run a supersonic clean, I already know that).

I've resorted to buying another printer as I have orders piling up so it's not time-critical any more, but I'd like to find a solution as it's an expensive printer and I've been very happy with it to date. A DIY solution would be ideal, but I'd be prepared to send the printer away if necessary (although I don't want or need to spend hundreds on it).

Any and all suggestions welcome :)