I suspect the problems you have encountered are a result of not having the latest version of the "ApprovedWorkman.exe" file properly located in the "Approved Workman" folder. (notice the space between the two words and the exact spelling) The EXE MUST be located in the Approved Workman folder along with a "Data" subfolder. If you launch the database from an old version of the EXE located elsewhere, or even if you launch the database using the correct EXE but that EXE is NOT located in the Approved Workman folder as it should be this will cause problems.
Regards deleting files from the USB flash drive that was used as a Secondary DB with checked out clubs... normally it is not necessary to delete the files but in this case I think it would be a good idea.
The objective is to be sure you have the latest EXE located in the "Approved Workman" folder. (be sure to include the space between the two words and make sure they are spelled exactly as shown) Also in the Approved Workman folder should be the Data subfolder. You do not want any other copies or old versions of the ApprovedWorkman.exe in these folders or anywhere on your desktop or on the USB drive where they might be launched accidentally. You also want to be sure that any destkop shortcut you may have truly IS pointing to the "ApprovedWorkman.exe" in the "Approved Workman" folder.