You're gonna have to be a little more descriptive about what's going on.... What kind of magic effect? What's the sound? Where are you? What are you trying to do?
It starts right after I begin a new game/load old one. I guess it has to be something related to mods because this is the first time it happens though I've played the game numerous times before. I made some changes to active mods list before starting the current game, but I'd rather find the easier way to fix the issue than to start building up the mods list again as they are working otherwise just fine and it's only a minor annoyance.
Pretty hard to describe it, since my english isn't so good, but it looks (and sounds) just like cast a spell effect, which creates a small purple puff around my character. Btw, I've checked the active effects list and nothing there seems to be the reason.
So it's only a small problem and could probably be easily resolved...