I'm sort of new to 'touching' the spider 4 120, I've had the amp for about a month and have been gigging out with it and I'm seriously considering making a custom cover for the knobs.  The fact is, the amp models and effects are so loaded that it doesn't take much of a touch at all on one of the knobs to seriously alter the tones coming out of the amp itself.  The quick cure (I think) is to switch to another channel and then back again to the one that got messed up.  If it's still messed up, then it likely got saved that way.  The next thing I'd try is power off, power on...if it didn't get saved, what you saved last time will load up when the amp turns back on (nice that it's solid state and you only have to wait a few seconds to be at full volume again after a power down).  I had to do that at a gig once, the microphone cord got pulled just enough to knock off my settings for the first song...ooops, power down, power on before things got too intense to do it.  I know that sometimes I have trouble with the tones, but I'm not sure what exactly it is that's causing it...what's cool is that with the mk2 shortboard (or express) using spider edit, all of your presets can be saved either as an amp bundle (for setlists) or as individual tones (for individual songs)  if you don't have a footswitch, you can't do that though.  The factory reset will wipe all of your personal pre-sets, and you (may) lose some pre-sets you can't get back without downloading (and again using the footpedal boards, one or the other) re-installing with Line 6 Edit.