EEA1 form - Full medical Insurance

Dear all,

Mine EEA1 as a student form was rejected twice.
The first time, I did not send anything relating to the Comprehensive Sickness Insurance, my fault.

The second time, I have attached my NHS medical card as well as NIN card. This is what I have found on this website that should be sent. They kept my application for 2 weeks so I thought this time I have sent everything what was requested.
Unfortunately they have sent all my documents back with the note that the FULL MEDICAL INSURANCE MUST BE HELD.
Now, I do not know what they are asking for. Do I need to buy a private insurace to fulfil their requirements if NHS is not enough?

I am a full time undergraduate student. Started my Uni in February and it is on going untill February 2012. I am from European Union and been living here for over 5 yrs by now.

Can anybody help me so my application will not be rejected for the 3rd time, please.

Thanks a lot.