Looks like the big quake in Japan has damaged some of their HF aircraft communications capacity.
Molokai Hawaii HFDL Groundstation alerting UNID flight of diminished HF into Tokyo on 11312U khz at 03:45z:
HACARS mode: 2 Aircraft reg: .N674US
Message label: RA Block id: G [Uplink]
Message content:-
42 DISPATCHER
** NO ACK REQ **
?IT SHOULD NOT APPLY TO
YOU. TOKYO RADIO HAS
DEMINISHED HF AT THIS TIME
BUT COMMUNICATION IS STILL
INTACT AND CLEAR. MY RELIEF
DID NOTE SEND YOU A MSG BECASUE
HE DET THAY YOU WERE GOING TO
ENTER TOKYO ON VHF
IF I GET ANY MORE INFO I WILL SEND
THAT TO YOU AS WELL
MICHAEL KARRELS/FLIGHT CONTROL