Yep I know what you mean, all sorts of nasties show up once you start cleaning
Seriously though...all that deleting the prefs folder will do is remove all of your options settings & if there's some kind of corruption in that folder, it could be what's sending your volume slider off into space sometimes.

If that doesn't work, try posting at the other forum. The volume control's only new since 4.15, so there might be some probs with that (just guessing).