iPhone 4 suddenly refuses to charge

My iPhone 4 was running low on juice earlier, so I plugged it in as usual. Was charging just fine for about 10 percent, and then all of a sudden a 'this accessory is not supported' message popped up on screen, after which the phone refused to charge. I tried two different apple charging cables and I attached it to my macbook and my pc, but it still refuses to charge. It doesn't detect the phone either. I noticed a little bit of fluff in the dock, so cleared that out, but no improvement.

I've also tried a hard reset (home and lock buttons being held), but no change whatsoever. I'm not sure what else I could do. The phone is still under warrantee, but I'd rather not take it in as it'd take several weeks before I get back.

Phone's never been opened, jailbroken or dropped so it can't be that.

Please halp me !