BIG UPDATE!
Seems one of the screws was damaged. Thus, i used the most obviopus solution; persuade by force.
Those mp4 were obviously not designed to cope with a damaged screw. I had to pull the cover off with the screwdriver. But, seems that i used too much strenght in the wrong spot, and...
Tadaaa!
Cell phone picture, not exactly good quality. Now i have to fix that ASAP =P