Digital BW, The Print

Hi there, I'm new to this forum so forgive me if this has been 
covered somewhere else.

For the past three weeks I have been attemtping to get neutral B&W 
from my 2100 using the Epson colour inks and Epson Archive Matte 
paper. My Eureka moment happened just before Christmas - neutral B&W, 
no sign of metamarism, great tonality and saved my sanity! The 
problem is that I now have run off a quick portrait session using 
studio lighting and these prints are back to having a slight 
green/blue tinge. Has anyone got any ideas why my outdoor shots 
produce true B&W but my studio lighting don't???

yours confused,


David