Never happened to me... only lag-related thing I've ever come across has been when my cursor clicks stop having any effect. I click on the ground and the green arrows pop up, but champ doesn't move; click on abilities, nothing happens; click on any other target, nothing changes. This would be all fine, but while this is happening, the game continues around me, and I can't do anything - once happened when I was pushing a tower at level 4 or so. I was just stood there while the minions got killed off and the champ and turret started focusing me, and then I died. This has happened only twice in total, and hasn't happened for a while, so hopefully it's been fixed somehow.