Q: When I try to open a CMYK TIFF or CMYK Photoshop file, I get an error "Could not open [filname] because of a problem parsing the tiff file" or "Could not open [filename] because of an unexpected end-of-file was encountered."

A: ColorSync 3 was installed on the machine when the file was converted from RGB to CMYK using an ICC profile and the profile was embeded in the file.
You should update your ColorSync to 3.0.1 and then convert the original RGB image to cmyk, or upgrade to Photoshop 6 which will ignore the damaged profile info in the file and open the image.