Pin13 LED not working

Hi there,

seems something on my UNO R3 isn't working anymore. The LED which is hardwired to PIN13 is not blinking anymore.
External LED connected to PIN 13 is doing it's job, so the 328P seems to be o.k.
The onboard LED is fine, too.
I followed the traces to a littel square SMD element, located beneath the quartz, having the 328p on the right side.
This device has eight pins. On the top left I measure some Volts when Pin13 is high. It seems that this thing is broken ... but what is it?

Best Gerrit

LM358 opamp/comparator.
1/2 used to compare Vin/2 against Vusb for voltage source selection.
1/2 used to drive L LED.
Not a MOSFET array.

Thank you for the reply. Do you think that, according to the symptoms, this could be the culprit?