I've heard that the Today Show appearance has tentatively been postponed until Thursday due to hurricane Gustav... I'll update if I hear more.
Update: This was posted at nkotb.com:
TODAY SHOW APPEARANCE POSTPONED DUE TO HURRICANE GUSTAV REPORTING. Due to the unfortunate, and unpredictable weather patterns in the Gulf of Mexico, the New Kids on the Block's performance at the Today Show Courtyard on Monday September 1st has been POSTPONED. Our thoughts and prayers are with the residents of New Orleans, Louisiana, Alabama, Texas and Mississippi, as well as all who have families in those areas. We are looking at dates to reschedule, and will make SURE our fans are the first to know. Apologies to all. -THE BLOCK