Do you have Advance combat logging on? Try disabling that and fiddle with the Network settings. Blizz mentioned some DDOS attacks yesterday that could have led to some issues. As @
Fretzur said; check if you get the freeze today as well. If so, turn off all addons in-game during play itself and check which addon(s) could be causing the freeze. If you are a DPS the group won't mind you in-game debugging so long you let them know. if not, try and get a grp with friends so that they don't mind while you tinker.
Also check the option to show LUA errors. That might help.