Yesterday, a glitch showed up where zones would crash a lot. On average, every half hour or so, you'd get disconnected. My guess is that something was rebooting, as it would take about a minute or so for the zone to let you back in. There was also a mild rollback of perhaps tens of seconds of lost gameplay, which is consistent with a crash.
This is obviously the sort of bug that games need to fix, and quickly. So last night, they pushed out a patch that fixed the problem. And created a new one: if you go into certain zones, you get disconnected with a "CommanderLoadFail" error message and sent back to the server selection screen. If you're in a zone with multiple channels, you can pick a different channel and carry on. If the zone only has one channel, you can't log on as that character.
I'd be surprised if they don't fix this tonight, as they're good about fixing game-breaking things quickly. But it probably wouldn't have happened if last night's emergency fix wasn't rushed out. I don't blame them for rushing, but this sort of thing is why it's dangerous.