Here is the knowledge base article that applies to your situation.

support.na.sage.com/.../viewdocument.do 

I believe you have data corruption.  We have fixed this type of error before.  If you need our help, please call us at 304-233-2612.

To determine if you have data corruption, open up a sample company, such as BCS -Bellweather Garden Supply and try the same process in the sample company.    If it kicks you out of the sample company, you could have a program related issue or incompatible Windows and Sage version issue.

You don't mention the Sage 50 version you are using or the version of Windows. If you are using an older version of Sage 50 below version 2019 and using Windows 10, you may just need to change your Sage ICON setting to run as an administrator and change the comparability setting to run in Windows 8. Try that first

If had the problem I would make a backup of your data, uninstall Sage and reinstall it to a new program path and data path, then restore the backup.

If that does not resolve the issue I can look at your data for no charge to see if it is data related.

Thank so much Kim. It resolved the problem perfectly. Thanks everyone for your support /response