I've had this issue too. If I am playing my Wii every day and looking at the various channels, it's never such an issue. However, if a few days or weeks pass without powering on the system, I can count on the BSoS* (even a non-WC24 channel, like I was going to play a GC game the other day, and it took a long time)
*I've decided to call it the Black Screen of "Swoon," since it's (as you said) not
dead, but merely swooning at all the WC24 greatness that is pouring through its circuitry all of a sudden.
Regardless of what you call it, though, it's ANNOYING.
edit: why is this in General Gaming and not in Nintendo Consoles??