After switching my development to a backup machine and back, I found that Xojo was trying to load all my external items by absolute path and asking me to find each one. A back of an envelope calculation of how long it would take was about 1.6 years including bathroom breaks and therapy.
Instead I opened my PROJECTNAME.xojo_project in a text editor.
Inside was many lines absolute lines like this:
Picture=LeftArrow;Macintosh HD:Users:stephen:Desktop:Stephen's CCC Backup:Users:stephen:Documents:Programming:OfficeTime:Code:Repositories:Desktop:officetime-desktop:support files:graphics:LeftArrow.png;&h0000000059B00640;&hFFFFFFFFBB07C4EA;false;0;&h0000000000000000
I did some search and replaces to get them to look like this:
Note the / instead of : for separators.
And voila, no more asking to locate files.
The above of course is using the Xojo Project, not Xojo Binary Project format.