Problem with buttons and USB conection

[Upa Mpx!]

Hi guys!
I think I have a new problem here. Some days ago, I tried to connect the audio output of my mp4 in the karaoke input of my sound system. After a few moments my player stoped playing. So, its buttons became crazy (they did not do anything but only the function select) and my PC did not recognize it like a USP drive.
After a few days, I found a full firmware compatible with my player and I recovered it. But when I installed the original firmware (with interfaces) the same problem continued: two buttons are not working, three has the same function of select and my player is no recognized like a USB drive. But if I left my mp4 only with the full firmware (without interface and functions) it can be used like a USB drive.
Can anyone help me with this problem? I do not know if some components (maybe the keyboard) were damaged.

Specifications:
Nano clone 1.5" with five buttons - 1GB.
Firmare 3.5.35 Wilson Co.
Like this: Mp4 Picture

[lattesurf]

Upa Mpx! , it is very likely that perhaps the karaoke input had done something to the player. i can't be sure what it might have done, but maybe the karaoke input had some voltage/current surge that could have "fried" some components in your player.