Arduino ADK - mega8u2 problem

Hi,
I got an Arduino ADK last week and yesterday I tried it with Samsung Galaxy S and it works but after some time I can't connect it to PC :s tried another PC and the same thing, nothing...

Basically the board works with the last arduino code I uploaded, I can connect the Samsung Galaxy and play with the led but can't connect it to PC so for some reason the mega8u2 broke.

I contacted the store but it said they can't get it back and that Arduino doesn't have any kind of guarantee, is that true? The stupid thing is that I have an Arduino duemilanove since 5 years and use it for all the things with any kinf of problems and it after some minutes broke... :S
What should I do?

Sorry my english :s

Are you sure it is the mega8u2 ?

You could try to program it over ICSP ...