Are sticks still read? Then it could be a power issue. Try an externally powered disk or a powered USB hub.
If sticks aren't read either, something might be wrong with the TV.
My LG LW6500 was recognizing external USB drives till a few days back. Suddenly it has stopped working. Whenever a USB is attached in either of the ports there is no message or response. It behaves like nothing has been attached. Can someone in forum help me overcome this issue. Please note that all my USBs are working fine & were actually opening. Thanks