Photoshop :: Help Files And Color Layer Merging

First, the help files, as of today (they worked before) have mysteriously ceased working. If I click on Photoshop Help, I get the error message "The memory could not be written." The same message appears if I try to reinstall Adobe Help Center, and when I attempted to reinstall CS2 entirely.

Secondly, the reason I needed the help files is because my color layer will (as of today) not merge with other layers. When I try to merge a layer set to "color" with, say, a "normal" layer, the color effect automatically disables as it merges, leaving a horrible mass of paintwork on top of where my nicely shaded color effect used to be. Now, I am certain color layers used to blend, as I've done this simple operation many times.

Reinstalling Photoshop CS2 hasn't fixed either of these problems, rendering it almost unusable (I use color layers a lot).