Invalid Credentials

Hello,
I have recently been getting an error with invalid minecraft credentials, I use a Mac Version 10.8.5. I use minecraft 1.6.4 and I keep getting invalid credentials. I have tried to log onto minecraft.net with the exact same credentials, worked 100% fine. Then I tried migrating to a mojang account, again 100% fine. I still try to log on and I get the same error. I have looked it up for the past 30 minutes, still no solution I have found. If anyone can do anything about this it would be great! (I have also tried changing my password, still no luck)

~Sonictj