Yeah, this is a known problem with the game. Issues do arise when trying to install numerous updates at once. There is a guide on the official forum about how to solve this issue: http://community.us.playstation.com/t5/Gran-Turismo-Series-General/Recommended-GT6-Updating-Instructions/td-p/44803188
There's not a lot I can say though... I haven't encountered this problem. I've been playing the game since launch and have been able to install each update one at a time. But I hope this helps!
As much as I like how much post-launch support the game has gotten (including tons of free cars and tracks) It is certainly a nightmare for those just starting out.
"Never argue with stupid people. They will drag you down to their level and then beat you with experience."
-Samuel Clemens
