No reason why our Monday edict to bring you coverage of other people’s NY Comic Con Coverage should stop us from bringing you the latest in celebrity news. Namely, why R&B star Chris Brown and sexy popstress Rihanna were absent from their Grammy performances last night, and why they canceled at the last minute.

UPDATED (below the cut)!

Above is the Whilshire Police Station in Los Angeles, where Chris Brown turned himself in, yesterday at 7PM…

From The Chicago Tribune:

Chris Brown was arrested moments before the 2009 Grammy’s were set to commence. The Los Angeles police department announced that Chris Brown, a double nominee and scheduled performer, was being investigated for allegedly assaulting an unidentified woman the night before. Brown turned himself in to authorities and was briefly held before posting $50,000 bail Sunday night, jail records showed.

Chris Brown and longtime girlfriend Rihanna also nominated, were both slated to perform in different slots of the show, but separately dropped out at the last minute. The victim of Brown’s alleged assault wasn’t identified, and it wasn’t immediately clear whether Rihanna’s absence was related to Brown’s.

Police booked the 19-year-old R&B singer and dancer on suspicion of making a criminal threat, a felony. Police did not explain how their initial report of an injury assault related to the charge, but it will ultimately be up to the district attorney’s office to decide what charges, if any, should be brought against Brown.

As of now, we have no new information about the assault. But if it turns out to be juicy, bad and ugly, we’ll keep you posted.

UPDATE: The Los Angeles Times (and thusfar only the Times) is reporting that Chris Brown assaulted Rihanna, his 20-year old girlfriend.