Re: Amplifier issue please help
My friend has this same problem with his Flextone 2.0. Line 6 told him that it was a matter of the computer inside the amp "clipping" the signal, which is what gives you those really quick vibrations that sound like a fart. It's digital clipping (which is a rapid-fire clicking noise) manifesting itself through the speaker. Pretty dangerous to the speaker.
How he solved it? He stopped using his guitar with active pickups through the amp. Problem solved. There was simply too much signal going from the guitar through the input into the computer component. Do you have a guitar with active pickups (does your guitar have a battery in it)? If so, use a guitar with passive electronics or get something to "pad" the signal from your guitar to your amp so it doesn't send a signal that's louder than line level.
If that's not the issue, then I haven't the faintest clue. I'm a Line 6 fan as well. Not the Spiders, though. My Vetta is awesome! Never had a problem with it and it cranks so cleanly!