My screen freezes for the first second or two of every ladder game i enter. The actual match is still going on because my opponents are not lagging, but i get this lag at the start of every game. I can select units and send them to mine while the screen is frozen but it takes a second for the screen to catch up. Only started doing this since the recent patch. I'm running all settings on low. My computer can easily handle sc2 (imac) so I'm pretty sure its not the comp.
I have this problem too. Seems to be the same as this thread: http://us.battle.net/sc2/en/forum/topic/6293819780
Theres been a few other threads mentioning it in mac forum, but I dont know if there is a consensus. I played a bunch of 1v1s today, and lagged in the opening of every game. Some games it only seemed like a second at the most, others it was like 3 seconds or so. It is quite annoying