I've uploaded an image to do the talking for me :)
How can I solve this?
EDIT: It might be helpful to point out that my problem has start with winopen not opening folders, and after some googling I've arrived at this error message I've posted.
Also, I've already tried to play all kinds of permissions, and nothing worked so far.
Lastly, this problem started after I've replaced my computer with a laptop. Both run Windows 7, both are 64 bit, and both run the same Matlab version (2013a), but for some reason, the laptop gives this error (and in case anyone is wondering, my code is 100% 'correct', because it worked on the PC (and other PCs for that matter) and has not changed ever since).