I've not had any problems getting 1000G in this game. The whole time I was playing I was worrying about glitches after reading all the posts on here. I got the unreadable disc error once but I just loaded up the game again and it was fine. The only tip I followed was that when I finished a mission I would do mini games until the 'the next story mission is now available' message appeared at which point I went straight to the next mission and didn't do anymore mini games until I finished that one. Do that and you will have no problems unlocking all missions.
If the last few mini games on each job doesn't unlock when you've completed the game, get all the flawless achievements and they wil appear.
I never had any loading problems, game freezes, corrupted save files or badges not unlocking. If you meet the criteria for each achievement it should unlock. Good luck.
Currently need boosting partners for:
Red Dead Redemption
Street Fighter 4
James Cameron's Avatar
Gears of War
Test Drive Unlimited
Need for Speed Undercover, Hot Pursuit & Shift
Mr. Driller Online
Kameo - Elements of Power
Guitar and Band Hero (can these be boosted?
TMNT 1989 Arcade
GOING FOR 100,000 by end of 2013!