Ummm... Worked for me when I modified an exported version of the detailed attributes, I modified the three columns:
v_products_attributes_filename, v_products_attributes_maxdays, and v_products_attributes_maxcount
I uploaded the file leaving Attrib-Detailed-EP as the beginning part of the filename (I had modified the text that followed so that I wouldn't lose my original export), I then imported the file (which had also been modified to update only a few records instead of everything) and what I had entered was transferred to the record associated with that particular attribute as viewed in the attributes controller.

So, I don't know what the issue is/was for you, but perhaps you could explain further the actions you took from export to import including filenames involved, error messages at the bottom of the screen just after import, etc...

So, if