Device stops working and hot after usb plugged in

[fagci]

This component too hot. Battery was plugged in, but switched off.

What it can be and what can I do?

// P.S.: gray wire is single tone buzzer, black wires is two buttons. All works fine earlier. Case was enclosed, environment was room. All wires are insulated with thermo tubes and isolation stripe between board and speaker. Buttons filled w/glue inside separated place of case.

// P.S.2: usb comes from my notebook, works good earlier too...