'Buffy the Vampire Slayer' Star Nicholas Brendon ... Arrested Again After Comic Book Convention

2:20 PM PT -- Brendon's rep tells TMZ, "Nicholas is, unfortunately, battling a disease that many of us don't understand. We are working with him to improve upon the situation at hand and look toward the future. He's sorry for his actions and takes what happened last night very seriously. We will take great care to ensure his safety in the future."

"Buffy the Vampire Slayer" star Nicholas Brendon is in big trouble ... he was arrested for felony grand theft at a Hilton hotel.

Brendon was in Ft. Lauderdale for a comic book convention and authorities say he got rip-roaring drunk, trashed his hotel room and ended up asleep in a hotel employee's office.

According to the police report -- obtained by TMZ -- Brendon did $450 worth of damage to the room and was on the hook for nearly $380 in food and beverage charges.

Cops say Brendon refused to pay, and that's why he's been charged with grand theft. Sounds a little like the whole Randy Quaid incident at a hotel near Santa Barbara.

Sounds like the convention folks paid for Brendon's room, but he was pissed he didn't get more, because just hours before his arrest he tweeted, "Hey Twatters! I'm stuck in Ft Lauderdale w/no per diem. No hotel. No ride to the airport. Thanks @Shockpopcc."

Brendon has had issues at comic conventions before this ... he was arrested last October for a disturbance at an Idaho hotel. Two days later, he apologized and said he was going to rehab.

A few days before the latest arrest, Brendon said he split from his wife of five months.