Digital BW, The Print

Hello,
I\ufffd m working with VM inks and Photoshop 6 with exactly the settings
recommended by Paul (PS 5 default etc). However, while things were working
the way they are intended to do, some days ago there suddenly was an odd
phenomenon: When I apply now no correction curve (like i.e. "neutral cool")
the prints look normal and correct, slightly warm, like the full spectrum.
When I apply the curves, the prints get much too dark... I checked
everything, I didn\ufffdt find what has happened...

Has someone got an idea?

Greetings Bernhard