This type of error stems from a corrupt data base file. Many possible causes. Since this product is no longer supported, I recommend restoring the file from a Backup. The corrupted file is most likely RT3.MDB.
After restoring the file, immediately perform a Repair and Compact process (https://sundialtimesystems.freshdesk.com/solution/articles/1000058931)
Once the Repair and Compact operation is completed, Open RealTime, Access Company Setup and "Select" your company again.
Once the Selection completes, Open Company Setup again and ensure that all your company settings are correct.