During importing the dataset why certain field is always asking about the "Undo changes"?

I've around 200 records dataset which already created by the datatable editor. After exporting the dataset and try to import it again from there it always come up with "Undo changes" for a particular field value.
I have more than 30 fields values and some are conditional ones(depend on the value of another field).
The field I am pointing out is also a conditional one and it's not the only conditional field.
Please let me know any clue to work out?
-Sanjaya