Digital BW, The Print

Hi all... I'm using the UT7 set in a 2200 and suddenly find myself with a clog problem I 
don't understand.  After changing a number of cartridges, I can't get a good nozzle check.  
Sometimes a couple of carts will be printing only partially, sometimes a number of carts 
will not print *anything*.  The nozzle checks don't seem to be making a progress but just 
shifting from fairly bad to terrible to fairly bad.  Can anyone help me to diagnose the 
problem?

Ed