Thanks, Zak
It is actually the "Place Photoshop Button" file banner.psd in the online adobe tv Muse "Katies" Tutorial [How to create a website with Adobe Muse | Adobe Muse CC tutorials]...I was trying to follow the tutorial. I opened the file in Photoshop, re-saved it and tried again, and it opened without a problem. Seems to be only while it is still encapsulated in the .zip file that came with the tutorial.
Regards
Roy