The previous post is on the right track. You might also try saving the file as a BMP or JPG(if you don't need the resolution) in some other program first.

One other thing that sounds like a stupid question, but are you sure the file is really a TIF file? Many programs will look throught the file to see what type it is, but Photoshop seems to actually use the extension to identify the file typ, then if it doesn't see what it is expecting in the file itself, it pukes.