i also have had issues last night with the game freezing while loading.
i dont know if it was coincidence or what, but when i turned off the external hard drive i had plugged in it worked no problems.
more realistically is what i ahbe read on a few forums about the freezing. apparently it is to do with the game accessing the servers online. even though you aint playing the game online, it is still connected to the net to update stats etc on the rockstar social club site. if the game is having any difficulties accessing these servers then it will hang and crash. apparently it can be solved by disabling the interent connection on the ps3 while playing the offline game. this has worked for some people, but it also hasnt worked for others.
this might not even be the issue, but its plausible.