Digital BW, The Print

I also have a flush cartridge in the PK slot.  And I usually print 
something 3-4 days a week.  

This current clog has become very persistent.  I have tried head 
cleanings (x3) then resting the printer.  I have puddled Windex on the 
parking pad.  And I have tried running a Windex-ed paper towel under 
the print head.  The nozzle cleared yesterday, I printed 2 8x10's then 
turned the printer off.  When I tried to restart it later in the day, 
the nozzle was plugged again.  I have tried all of the above again 
plus just printing through that one nozzle (using QTR to turn the 
others off).  I have now removed the cartridge from that nozzle and 
replaced it with a flush cartridge.  However when I try printing with 
it, no ink comes out so the flush fluid isn't making it to the head.  
The Windex is puddled on the parking pad again and I wait ....

Jenny