I do not know what the situation you are in. 
 
if you did not live in Canada for the 2007 entire year,  you should show them you are s non-resident in Canada in 2007 if you have claimed, filled out  a non-resident form, and  have been approved, you should not claim your tax income in U.S.
 
 If you did not have a non-resident form, you might ask them if you are able to fill out now.