Are you using Zip Compression when you save as Tiff in Photoshop. Many Tiff viewers are unable to view zip compressed Tiff files, including DPP.
Either use None or LZW and it works fine in DPP.


I have also noticed that if you use Save for web and devices rather than Save as and use Jpeg compression DPP won't read them either.





Photoshop CS4 and earlier you do have to convert from 16 bit to 8 bit before saving to jpeg. (Image / Mode / 8 bit/channel). This is a step a lot of people thought was unnecessary since jpeg is 8 bit anyways. Adobe listened and now Photoshop CS5 allows you to skip that step and just got to Save As or Save for Web and Devices. When it saves the file it will automatically convert it for you.