This used to work fine but on the MAP YOUR FIELDS section drop down menus do not work. when i select to map contact email to the column called  email I get a popup saying " This field is already mapped". 

It has not already been mapped. I have tried importing the file in other formats such as .csv and. xls and i get the same problem. It works if I switch to Firefox, but not Chrome.

As i said it worked before, has there been an update which has caused this glitch?