Digital BW, The Print

Hello,

I've just purchased EZN inks to use in my Epson C86 printer. 
The image appears fine in Photoshop Elements and looks fine 
in Print Preview. However, when I print the image, parts of the 
image appear as normal, but some parts are appearing as 
though they are negative-like i.e. the opposite tones to what they 
should be. Has anyone come across this problem, and if they 
sorted it, how did they do it?

Thanks.