User blog comment:Bleeh/Error: Glitchy Sims with OS X Lion (Mac)/@comment-62.31.36.157-20111130091901/@comment-26744861-20111130105930

I see your point but if it worked fine for someone else before they upgraded to OSX Lion (which I've heard is pretty buggy) then Apple obviously changed something to do with graphical rendering, which obviously causes the graphics glitch to come in.

tl;dr? Blame both.