1. Replace all double quotes with single quotes. Presence of the double quotes seems to break the parsing and causes the import to fail.

They had a lot of double quotes in the text ( probably SQL statements relating to the test cases), these were breaking the parsing. These has to be replaced

2. Change "Description_comments" column to have two more words - something like "Mapping document" to "Mapping document located at". This will help Mingle recognize this column as a description instead of a property.

They wanted this field to be taken in as "Description", however Mingle would not do as the data contained only 2 or 3 strings. Mingle does not add a column which had less than 3 strings as Description. In this case the error relating to characters was because , even though the data contained not more than 3 strings the characters were more than 255

For example : 

"Mapping document: 

\\sfRd6\ITSERVICJ\B 2010\04 Feature\01 Data \ODS Deliverable\Presteps to Staging Mapping\Member\Member_story_Mingle_526_Source_to_Delivery_Mapping_20091124.xls"

So 

1. Having less than 3 strings caused Mingle not to take this column as description but instead considered it as a property.

2. But this property had more than 255 characters.  

Solution was to add more strings.