z3100 travel success and failure

Hi guys

My printer arrived in London and I got things set up over here relatively simply ... however there is one problem remaining

As per my earlier post ... printer arrived after 9 months unplugged. Heads and cartridges had been removed.

First I installed new ink cartridges. Then I installed the old heads in the hope that any gunk from the lines would clog up the old heads. After a clean cycle and some prints (about 6-10ml from each lines) all was working wonderfully so I decided to change/replace those old print heads.

In turn I replaced all of them ... all work well except the matt black (red is fine) which is consistently blocked up despite cleaning and in fact looks like it is even getting worse. These colors had used bout 5ml each before I had taken the old head out.

Anyways ... would like some advice to help solve the problem if possible.

Many thanks

mehdi