I can't understand why this issue even exists as of now. It seems a glaring bug in CR, to be unable to correctly map the data type. I tried altering the column type to "text" in SQL Server. After doing this "Verify Database" prompted me to map the newly altered column, but would not list the column in the list of candidates on the right (yes, I unchecked "Map Type") If I click on "OK" in the "Map Fields" dialog the field are removed from the report (not acceptable.) If I click on "Cancel" in the "Map Fields" dialog the field on the report are still typed as "string255" If I "Verify Database" a second time the field types are finally shown as "Memo" and the report performs as expected.
I would simply suggest that all the varchar(max) attributes in the migrated db be altered to "text" datatype, except that SQL Server has made it quite clear that the "text" datatype should replaced by varchar(max) and that it will be discontinued in subsequent SQL Server releases.
In other words Crystal Reports 12 supports the older mapping not the newer. If that's not a bug, what is?