In their present iteration, all of the PK modules will only work if a pixel-bearing layer is targeted at the time of selection. It does not have to the BG layer, just not an adjustment layer. I assume PixelGenius will fix this.
Re print centering, I can't say why this used to work with Windows. It never did on the Mac. Epson's drivers specify non-uniform page margins in all of the stock page sizes. (Bigger margin at the bottom.) But to solve, all you have to do is set up custom pages with equal margins all the way around. Once done, just select the custom page and the print will center perfectly.
Paul, does this comment apply to PK Sharpener? I know the Background Layer needs to "exist" and be switched on for PK Sharpener to work in CS2, but as you say it does not need to be "selected" in CS2.
Have you made any progress on the print-cenetering problem using CS3 with the Epson driver? That is a matter of serious concern and unless there is an easy work-around would deter me from installing my copy of CS3 until it is resolved. It defies belief how Adobe could release software with this kind of defect. I wonder whether anything else is going on in your system that may be causing it - say something knocked by the install, (which as we've read has not been a smooth sail for many folks)?