some things to check, test and try:
Is the sheet name/number really starting with a comma? Audit the sheet with the table, audit all the sheets that are fubar. Use the SSM resave all sheets function. Restart C3D and the computer.
Verify the sheets read the proper data in to the sheet itself. Create a new blank sheet, add it to the set and see if it can reference the sheet set for the names, numbers and descriptions of the bad sheet in plain text fields. Try the sheet list in this new file. Copy the entire sheet set file and some of the data files (good and some bad files, but all in the same action) to another folder and test the table in the new files.