Deploying mex functions using the deploytool

I'm having some troubles using the deploytool to create a solution that has to work in conjunction with a third party mex function (in this case vl_sift from the vlfeat library).

I have the following function :

%%%%%%%%%%%%%%

function [] = Sift(im)

warndlg('Entered function'); % for debug purpose

figure,imshow(im);

try

p = vl_sift(single(im)); % vl_sift is a mex function

warndlg('Sift is OK');

catch exception

warndlg('Sift Failed');

warndlg(exception.message);

end

end

%%%%%%%%%%%%%%%

when i call this function from a certain other function and deploy the code I get the warnings "Entered function" and "Sift is OK" , which means that the code worked fine. when i try to call it from a different function (a gui code) and deploy it exactly in the same manner (as far as i can see), i get the warnings "Entered function", "Sift Failed" and "Invalid MEX-file '...\vl_sift.mexw64': The specified module could not be found" ('...\' is the full path to the mex file).

I deploy the code exactly the same in both cases, yet, the mex works fine in the first and doesn't seem to be found in the second.

Anyone has any idea what could cause such a behaviour ?

Thanks, Michael.