Andrew,
Thank you so much for putting it so simple! Now I got it. I thought Photoshop would just use the RGB numbers, just like any other application.
And I believe the color mismatch I'm having with exported TIFFs from Capture NX that are opened on CS3 has something to do with my dual monitor setup. Maybe Capture NX is loading the profile from the primary monitor, from where it is first started, and using it on the secondary monitor, where I do my post processing work. Is that a possibility?
Best regards,
Luis