Nisant
I got the same letter couple of weeks ago.
I called in and my wait time was 2:15 mins( I m serious) and then he asked me lots of questions like my previous address 
and he asked me what was the amount on last years tax return on page 14, 55, 85 etc.
Its been more than two weeks but i have not received my money yet.
I will keep you posted if I got my refund...
but make no mistake, its because u an I provided two different addresses on our taxes of 2011 and 2012


Gud luck  ..