Halo 4 fans who have been having issues playing online due to an apparent partial ban will have an update from Microsoft soon. To recap: when the Crimson Map Pack arrived on December 10, 2012, confusion ensues momentarily as people realized they could download it for free. Turned out, this was a make-good gift from Microsoft following complications in November with the publisher's "14 Day, Buy and Play" program.
In short, Crimson launched as a free-to-sample download on December 10, with a ticking clock meant to turn off access on December 18. Unfortunately, it seems that some players -- even those with a legitimately purchased War Games Map Pass (read: DLC season pass) -- are being barred from Halo 4 online play, or certain parts of it (via Kotaku). A growing forum thread at Halo Waypoint was updated over the weekend with a note from the moderator promising a fix soon.
You can read the full text of the statement below, but the gist of it is: players are not being permanently banned for checking out the Crimson pack. The issue is being investigated, and an update from Microsoft should be issued sometime today. Read on for the same message presented in a more official way.
We are not permanently banning players for previewing or purchasing the Crimson Map Pack. We are currently investigating the recent reports of permanent matchmaking bans.
We will provide further updates tomorrow. Thank you for your patience.