Panasonic EB-A101 refuses to detect SIM card. Error: "Please insert SIM"

Hello. I bought the new EB-A101 from Shanghai, and have been using it
in Australia for two months without problem.

One day after entering my SIM pin, the unit defaulted to Chinese, and
said "Please enter SIM". I have confirmed that

- the SIM is not faulty;
- I definitely have GSM coverage;
- Other SIMs also get the same response;
- the SIM is making adequate contact with the pins;
- there is no obvious hardware reset button.

I have read about SIM lock, but this seems to be a different issue. I
suspect the unit is faulty, but is there anything I can try before
shipping it back overseas? Thank you.

cw
.