It is not on xbox yet, here's the writeup:
Grand Theft Auto Online Launch Updates
Some have answered that this fixes the bug when trying to race Lamar in the first mission (first mission spoiler). But be warned, others have said that this freezes their console. A possible fix is to wait for 30-40 seconds after the update prompt pops up after booting the game. People on other forums have reported that this works.
Lets hope this helps, especially those of you that haven't been able to enter the online at all.
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