Soft Shadows and Color Shift

[Rob Briggs]

A few weeks ago I had a problem with 100% cyan showing up with a black screen on my RIP.
Jay with Multi-Ad called and said it could be a preference for "convert RGB to CMYK".
When I unchecked this pref everything was fine. 
However he also told me he has seen this same problem on ads containing soft shadows.
Unfortunately we have seen this problem now too. 
We just printed a red & green Christmas section. 
To simplfy things we use the cyan plate for the spot green and the magenta plate for the spot red.
All of the ads that have soft shadows had a color shift putting black and magenta into the cyan elements.
There was also a black screen put into the magenta.
Needless to say, we now have a red and muddy-grayish-brown Christmas section.
Is there anything I can do to avoid this other than just not using soft shadows (which by the way is the only reason we upgraded to 8.0).
We are using 8.0 on XP.

Rob Briggs
Production Supervisor
The Medina County Gazette
330.721.4081