This error means that there is a character in your data that they system can't process. Look for any unusual characters in your content, especially characters that were copied in from another source, and try typing over them with the correct character. 520 tags are especially common culprits. If the error message mentions a "0x1F" character, that is an invisible delimiter character, either restart the record, typing your data in directly, or send a message to bibchange@oclc.org with the number of the record in your Online Save file. Sometimes they can identify the bad characters and clear them out for you.