Well I just logged in to play on Argent Dawn, my main server, only to find I apparently have no characters on Argent Dawn, go figure.
I could have sworn I had about 7 characters on Argent Dawn, including two level 60's.
Fear not, Blizzard is aware of the issue, which is apparently affecting Magtheridon server as well.
Oh and Blizz, if in fact you did accidentally wipe all he characters off of AD, when you are restoring them, remember, my level 60 hunter had 8/8 Cryptstalker, the Baron's epic mount and 1000g in the bank.
Oh and a crimson whelpling.