Yep, this is a universal problem that has become worse since 1.06 update :-( The lockups that people experience are the worse part. This is where not only the game freezes but when the PS3 also locks up and the only solution is pulling the plug and then having to go through the mundane operation of rebooting and all the file reconstruction process.
Some nights are worse than others but we have found that it can be reduced by doing a few simple things.
1) Start the session off by going to another track first.
2) Once at Bathurst never stay in the lobby. Either be on track, in your garage or tuning screen
3) Also the chat is clear in these screens as well so do your gasbagging from there
4) Boot anyone that shows the slightest bit of lag (not conducive to making new friends though)
5) And from personal experience, just give up after the 3rd lock up, it was just not your night ;-)
Why does it happen you ask, it's because GT6 is a broken, half assed, incomplete Beta release game that has been cobbled together by a company that just wanted to squeeze the last few dollars out of their fan base on a superseded console. They have our money and they don't care!