Very interesting indeed, having had a look through the scheduled log and mail logs I can see the mail left this morning at 4:30am and that you and a whole pile of others are in the list for emails being sent today.
I suspect this is due to the time difference between US and Australia, up until recently daily digests, birthday emails etc would leave at 9am. As anyone could appreciate the busiest time for an ISP is around that time with everyone jumping on for the day doing whatever they need to so I had to change it around.
My thinking of what's happening is when I changed the time I perhaps may have setup the job 24 hours later than what it's meant to be, I could never really read the time
I guess this would also be causing some problems for daily digests as well?
Thanks for bringing this one up.