Asus xonar no frontal sound

Hello. First of all, sorry for my English, is not my first language.

The problem with this sound card is that i don't have sound in front speakers output or in the front panel output for earphones. It work for 1 month, and then stop working. Tested on other computers, with XP (I have Win7 ) and Suse Linux, it work perfectly. I put it again on my first computer, and.. it work! but only for a few days. Now, nothing sounds on front speakers. Anyone have a similar problem? I need to change it at the store?

Thanks for your time.