Just an update for those who have interest: I reported the problem on the LG website and the LG guy came yesterday -- surprisingly quick. Problem solved: he changed the main circuit board, get rid of the ice accumulated around the fan. The best thing is: free. The guy told me that my fridge is almost seven years old (based on the serial number; I don't have the receipt). For that age fridge, the only thing within warranty is the compressor (seven years). But LG provides a once-a-life circuit board upgrade (no matter whether it is within warranty or not). They also changed the light set for the cooler (again, free since the original design was not good and there have been lots of complaints.) Thanks for your advices.