Har du kolla länken till Line6 så du inte har något av de chipset som nämns?
"Chipset Error Explanation: If the computer fails to meet standard USB requirements, a possible result the soundcard creates a "white noise burst" at the analog audio outputs. This is caused by a flaw in some USB chipsets that were manufactured by Intel using the ICH6 architecture. The chipsets we have verified as having this problem are the 915G, 915P and 925X chipsets, although others may be affected as well. Intel publishes on their web site an Errata that provides a more detailed explanation. Please note that computers that create this problem produce problems with all USB 1.1 audio interfaces, not just those manufactured by Line 6."
http://line6.com/support/entry!default...SearchPage=true