It looks like you want the product of the matrix (in the second part) with the vector (in the first part). The problem you are having is that the columns of the matrix are not in the same order as the elements in the vector.
Read in the investors and the y vector from data set A. Then use the INVESTORS vector to specify the order of the variables when you read the matrix, which I assume is in a data set named M:
proc iml;
use a;
read all var {investor y};
close a;
use m;
read all var investor into X; /* read variables in order contained in INVESTOR */
close m;
v = X*y; /* matrix-vector product */
print v;