In your Quark color pallette, do you have only one black, or has someone created another one using cmyk or a percentage of black? Go to edit>colors and choose your black. If there's more than one, select and edit, and check the color breakdown. Acrobat is not likely to add color or screens where there is none to begin with.

I don't know if this will matter or not, but you might also want to check your Quark color management preferences, and make sure they're not active.

Jim