Do you have Norton anti-virus or 360 on your PC ?
Hell no, none of that crap on my system

Only thing that I normally have running is a firewall. But I completely closed that (not just disabled but actually closed the thing entirely).
I think I kept the previous version of MultiBit somewhere (before I updated to 0.4.14). I will restore that and see if that still works (never had any problems with it before).
I'll check for anything else occupying port 8333 as well, but I doubt it (got no other networking background stuff running).