My stats say differently, Chrome is at 12.9% and hasn't gained ground in over 3 months.
I did notice however that the latest version of firefox is controlled by IE under Windows7. Open your IE browser and under internet options set you LAN settings to resolve to IP 0.0.0.0 and only IE SHOULD be unable to connect to the internet but under Windows7 those IE settings knock out firefox too. That wasn't the case in previous versions. Since Firefox is controlled by IE now I wouldn't be surprised to learn we sometimes receive the wrong data.