Have you checked the content of this property right after you load it from database? What is the mapping of this property/field?
By default, string properties in Aurelius are mapped as VARCHAR, and by default the length of such field is 255, so my guess is that you are simply saving a value that is longer than your underlying database structure supports.
If you want to save text with "unlimited" size with Aurelius, better map it to a TBlob property or map the column to have 65536 chars: