HI Alfonso! 

thank you very much for your reply.

So, I cannot open the 3d files generated from the 4d conn output, this last I can open, though. 

In mricron I receive the following error message:
Warning: the header file is not in nifti format [the first 4 bites do not have the value 348]. Assuming big-endian data.

In spm12 display function I have three black windows. But again, I can see the 4d conn output.