Uh oh.

I got home today and powered the Wii up to play Lego Indiana Jones with my kid. Upon turning it on, it produced a solid black screen and said "Now repairing....DO NOT POWER OFF."
Does anybody know what the heck I do now? I can think of only one thing that happened, that somehow or another the NAND became corrupt....or that perhaps it tried a menu update that failed.
In either case, here's my worry - Bootmii is on the machine but not as boot 2; it's stored as the other thing (whose file name I forget). I do have preloader installed and have been more than able to get to it to copy and check the nand files with this current setup, and I do have a copy of the most recent NAND on my CPU so I'm not TOO worried about it being dead.
My concern is that I don't know how long I should wait for it to come up with a different message. In talking to my wife - and what I could get out of my daughter (she's only 7, so I wasn't accusing her of anything, just asking if it did anything wierd), neither one of them can recall anything strange happening with a game or the unit when they played with it a day or so ago. Given that it's been in this state anywhere from 10 minutes to 24 hours ago.
Has anybody seen this error before? How long should I wait before powering it down and seeing if I can fix it with preloader and bootmii? I did unplug the hard drive to make sure the message was coming from the Wii itself, but it suddenly dawned on me that could be the only situation, potentially, unless a game file on the drive went belly up.
What do you suggest?