You may have run into this issue when using the MySQL Group_Concat function, or perhaps when retrieving a record with a very large text column.
If you determine your columns length,
<cfoutput>#len(myquery.mycolumn)#</cfoutput>
You are presented with a disappointing "64000".
Don't despair, this is actually a default setting when you first created your Data Source in ColdFusion Administrator.
Hop back into the Administrator, choose the Data Source, then Show those Advanced Settings.
Try upping your Long Text Buffer a bit, as shown.