Furious with several calls, Cuban went onto the floor to vent directly to official Joe DeRosa. He then stared down and screamed toward commissioner David Stern and a group of league officials, from the court, then the stands. He later used profanity during a postgame session with the media.
Announcement of the fine came hours before Game 6 of the NBA finals in which the Mavericks trail the Heat 3-2.
Cuban said Monday he was bracing for the fine, his second this postseason. He also was assessed $200,000 during the second round for going onto the court and for an entry on his blog criticizing the way the league selects officials for the playoffs.
Since buying the team in January 2000, Cuban has been fined at least $1,405,000; he's matched every dollar with a charitable donation.
The exact total of his punishment tab isn't known because the league doesn't always publicize punishments against team owners.
The league said it would have no further comment on this matter. Cuban did not immediately reply to an e-mail to The Associated Press.
Earlier Tuesday, Cuban posted a blog entry in response to a column in the Miami Herald that quoted him as saying, "The league is rigged" during his tirade after Game 5.
"That's a complete insult to the players on the court and the incredible amount of effort they put into preparing for and playing the games," he wrote. "The NBA couldn't rig the games if it wanted to. And it doesn't want to. It's that simple."
He wrote that he hates the idea of any wrongdoing, calling each theory "a business hole I have to work harder to dig us out of."
His solution: better explanations by the league of what happened and why.
"I think it would help the perception of our game," he wrote. "I think it would help fans better understand not only the rules of the NBA, but also the nuances, strategies and challenges of the game."