Hi guys.
Just to let you know that I've also solved my issue by replacing the USB Controller chip and the USB Port.
This topic was very helpful and I hope all of you can solve your problem as well.
I bought a CY7C68013A-56PVXC (I didn't buy it directly from the Line 6 distributor, I bought it from ebay) and it worked nice.
For those who believe it wouldn't work because it should have a firmware pre instaled, actually it needs a firmware but the firmware isn't located in that part so you don't need to be worried about buying directly on any Line 6 distributors.