Why in my laptop I can't see my SD card files anymore?

[AC Question]

Hi guys,

Today I upgraded to KitKat 4.4.4. For some reason if I plug my Samsung Galaxy S4, Android File Transfer doesn't show any content on my SD Card, just empty as brand new. However if I check it with Astro File Manager everything is still there.
Furthermore if I add a new folder on my SD Card via Android File Transfer it is shown on Astro. I tried with 2 different Macs (no PC...) and 2 different cables, still nothing is shown on my laptop.

Any ideas on how to make it to show up again? Everything is still there, and working, but I can't do anything with my laptop...

Thanks!