was allegedly kicked out of the Hard Rock Hotel and Casino in Las Vegas last week, after security thought they caught him counting cards while playing blackjack.
So-called "sources" say security "swarmed" the table while Ben was playing, and told him, quote, "We have to stop you, because you're too good."
Ben hasn't commented, but there are reports that he was banned FOR LIFE. Supposedly, the casino ONLY banned him from the blackjack tables . . . and is otherwise cool with him being there, and playing other games.
In a vaguely worded statement, a casino spokesperson said, quote, "Mr. Affleck, a valued guest of Hard Rock Hotel and Casino, is not banned from our property and is welcome back any time."
The practice of "counting cards" is NOT illegal . . . but obviously, it can create an advantage over the House, so it's frowned upon by casinos.
It's unclear how much Ben was up at the time . . . although he reportedly made $800,000 at the same casino in 2001, by playing three $20,000 blackjack hands at once. (Here's a video report on the alleged blackjack ban.)