Gran Turismo 5 was released yesterday, but there have been tons of complaints about the game's need for a persistent internet connection - something which the game's servers can't cope with right now.
If the game can't connect to the servers, it causes menus to lock up and sometimes for the game to even crash. According to Polyphony, the structure was set to handle 500,000 connections at the same time, but this has been greatly exceeded.
However, according to the game's creator, Kazunori Yamauchi, fixes are already in the works and there should be an update released this Saturday to help alleviate some problems. This will continue until they feel the game is good enough.