We're in day three of MLB 2K10's release, and also day three of MLB 2K10's multiplayer problems. While player-to-player game invitations are said not to be involved, many are having problems connecting to ranked matches. The solution requires a patch.
That's according to a 2K admin as of today. What happens in ranked match connections - I can confirm this as of posting time - is players are unable to advance beyond the pairing screen or back out of it. The only controls that work are your team selection (trigger/R2 L2) or uniform options (bumper/R1 L1). If you're stuck in this void, you have to quit out of the game entirely and start over, or wait until you lose the connection with your opponent (at which point your game reboots).
The admin says 2K Sports' dev team "has found and fixed the problem and are already in the process of preparing a patch to smooth out this experience." If I'm reading this correctly, if it depends on a patch and it's not some kind of network issue on 2K's end, it could be weeks before we get a definitive fix. They say that some have had success, after much persistence, of connecting to an online ranked match, and that invitations to friends are not affected.
NBA 2K10 was saddled with connectivity problems in all of its multiplayer versions from launch. I've heard they were attributable to capacity issues on an infrastructure dating back to the Dreamcast days. 2K Sports' problem is now more than four months old. And, apparently, it's now taken on a dimension involving a game's code. Not good.
Online Ranked Games in 2K10 [2K Sports forums]