Digital BW, The Print

I use an Epson 1280 with the MIS VM hextone inkset.  I recently came 
back from a 10-day vacation, during which the heat was off in my 
house.  I ran a nozzle check, a couple of cleaning cycles, printed a 
print, and then checked the nozzles again.  All the inks but one 
cleared up nicely on the nozzle check, showing the normal 4-line 
diagonal pattern for each ink.  But the lightest gray ink is only 
showing the two upper lines.

I tried the Windex-on-the-sponge trick (from the Piezo website).  No 
help.  I then tried the more drastic cleaning, removing the "color" 
cartridge and blowing Windex through the print head via a plastic 
tube (stopping well before any air got into the print head).  I 
believe the lightest gray is in the yellow position, which is the 
rightmost intake tube in the print head, as you look down on it. This 
was followed by a couple of cleaning cycles.  

This got the lower two lines of the light gray ink partially 
displaying, but then they went away again after I printed a couple of 
small purge patterns followed by more nozzle checks.  By then I'd 
exhausted the ink cartridge and switched to a new one.  A second 
Windex treatment had no further effect.  

The funny part of all this is that my prints look OK.  I'm probably 
losing a smidge of highlight detail, but it doesn't make that much 
difference.

Any thoughts on how to proceed?  Just keep printing and hope the clog 
eventually dissolves?  Use Fantastic instead of Windex?  Buy some 
Epson color ink and print color for a while, hoping the native ink 
will dissolve the MIS stuff?  I'll send it in to Epson if I must, but 
I'd rather not if I don't have to.

Thanks for any advice
--Peter Klein
Seattle