Ive just baught myself some videologic 7.1 Speakers. In the manual and in the box it says you can get a full 7.1 output with only a 5.1 sound card. Everything is perfect but after having them on for 5mins, the 2 rear speakers go fuzzy and distorted. Has anyone had this problem before? Or can someone enlighten me on how I could fix it without buying a 7.1 sound card.