Oh, i also got the same problem with my k81DJ before. But that only happened like 1 mth before my warranty ended. Sent back to the local distributer for repairs. Basically, they claim some wire had broken inside and they will solder a new 3.5mm plug for me. And for free since its under warranty.
The catch now is that, the new plug they will solder for you is just some cheapo plastic looking one. So you can say bye bye to seeing the gold plated tip already... They can source for one for you though, but the repairs will take longer and they will charge you extra for that.
Anyway, all this was based on my experience back in May this year. Things may have changed. Gd luck to u, pal.