Freezing in game

To start I'll say I play Sona often since she is my favorite support. It was the first time today playing her and I was doing fairly well up until about the 10 minute mark. Randomly I was frozen just shy of the grass in mid lane. I tried everything to move, including spamming clicks/spells/attacks and nothing worked to move me. My ping was about 30 the whole game so I doubt it was my side. Then I would disconnect until I died, then once I respawned I could suddenly move again. This happened a couple more times throughout the match, by then we just decided to surrender at the 20 minute mark despite doing so well. Not quite sure what happened, but if you could look into it or offer advice that'd be most appreciated. Just so you know I was playing on a OS X client version of the game.