A C5 error has 2 common root causes:
1 - It most often relates to Windows and a printer driver problem.
2 - A corrupt Memo field due to a server shutdown, frequently due to a power failure.
1 - Set your default to a different printer and retry printing. If you have the same C5 problem then it is likely a problem with the Memo field.
2 - You will need to run a file maintenance process; click the Utilities tab and select the Low Level Table Header repairs selected. This also might require a specialized process called a MemoScan.