Norm( {convex} ) error

Hi I got following error when want to minimize a convex problem

  Disciplined convex programming error:
         Cannot perform the operation norm( {convex}, 1 )

    Error in ==> MetricCVX at 29
              minimize(  norm(C,1) + (0.1 * norm(E,1))  - (0.2 *A) );

here is my code :

  D = 12;
  N = 6;
  Y = -1 * rand(D,N);
  C = zeros(N,N);
cvx_begin;
variable M(D,D) ;
expression C(N,N);
cvx_precision high
A = 0;
for i=1:N
    for j=1:N
        if i==j
            C(i,j) = 0;
        else
            %C(i,j) = exp(- (Y(:,i)-Y(:,j))' * M * (Y(:,i)-Y(:,j)));
            C(i,j) = - (Y(:,i)-Y(:,j))' * M * (Y(:,i)-Y(:,j));

        end
    end
end 
for i=1:N
    for j=1:N
        if i/64 == j/64 
            A = A + norm((Y(:,i)-Y(:,j))' * M * (Y(:,i)-Y(:,j)))
        end
    end
end
E = norm( Y- Y*C , 1) ;
minimize(  norm(C,1) + (0.1 * norm(E,1))  - (0.2 *A) );
subject to 
   M >= 0 ;
 cvx_end;

Perhaps you meant

minimize(  norm(C,1) + 0.1 *E  - (0.2 *A) ) 

That is convex and accepted by CVX. You already took the norm to get E in the line above.