Can you post some screenshots here to show the configuration of the Picture hotspot style (in the Style section) and the Hotspot properties (in the Tour section) for one of these pictures.
I actually just figured it out> I would call it a "bug" cause it sure "bugged" me
Here's what happened:
I created image hotspots using "add picture".
In my "styles" I had created two "Default Picture spots"
I assigned a file in the display parameters of Spot Style 1 but by accident assigned the file to hotspot 2 also.
This messed up PTP and caused the error.
So it was just a matter of having two Default Picture Spots with files (the same) assigned. IMHO if having two default picture spots, one should override the other correct?
I am still running tests but removing one file reference seemed to solve the issue.