I know this is an old thread, but I wanted people to know what worked for me if they get this error when they google search it.
I found that the length of the path to my robot cell was too long. My company uses OneDrive and the total path length to the location of the MyWorkcells folder was too long ("Onedrive-super-long-full-company-name-inc/Documents/Myworkcells/Project/"). RoboGuide didn't give any warnings though.
Once I put the workcell in a shorter path folder, like "C:/Customer/Project/" the error didn't come back.
So give that a try before some of the more extreme methods. I was using RoboGuide v9.4.