Saved Tiffs will not open in CS2 and generate a "Could not complete your request because of a program error".
These files will often open in Photoshop 7.0.1 or in CS1 but not in CS2.
The trouble may be caused by bad dates in the EXIF data and can originate from an incorrectly-programmed digital camera; or from a scan that was created after after Jan1 of this year (because of a known bug in some scanner software).
If someone runs into the "Could not complete your request because of a program error" problem, and does not have CS1, try opening the Tiff in TextEdit.
The EXIF data is right at the top. Check the EXIF data for bad creation dates and change any incorrect ones there.
Save and close; and then the file will probably open in CS2 without a murmur.