I'm sorry if I'm posting a duplicate thread on this subject but it seems that the thread
http://arduino.cc/forum/index.php/topic,40299.0.html
is read-only and I'm having the same problem (although I'm running 32-bit MATLAB).
Is there any known solution?
Thanks a lot in advance
Have you checked the README.txt included in the zip file with the target for Simulink? You will need to be using the specified version of the arduino software and one of the supported boards also listed in that file.