Digital BW, The Print

I am using MIS UltraTone CFS system on my Epson Stylus 1200. It 
worked prefectly fine until 2 days ago when one of the nozzle on the 
Light Magenta got clogged(a single gap found in the nozzle check 
pattern). I have never removed the CFS cartridge since I installed 
it, so I assume there should not be an air get inside the cartridge. 
I also use the printer almost 5 days a week. I have done so many 
cleaning cycles(6 cleaning cycles in a row, and again) and purging 
pattern printings(more than 6 letter size pages), but still can't get 
that nozzle unclogged(the single gap still apppears in the Light 
magenta nozzle check pattern). Without that nozzle, I can see lines 
in the shadow area on the printings.

Done anyone of you have any idea how to unclog that nozzle without 
sending it back to Epson for service? I have a perfect nozzle check 
expect the single gap in the light magenta.

Thanks