Why was Batman arrested?  More details come to light.  From UsWeekly...

Christian Bale lashed out at his 61-year-old mother after she insulted his wife, Sibi, London's Daily Mail reports.

Citing "sources close to the actor," the paper claims he "flew off the handle" at London's Dorchester hotel Sunday after Jenny Bale said "some outrageous things."

The source added: "Christian was stressed, but he didn't lay a finger on anyone. He just got very loud.

"Christian's attitude is that this was his mother's fault because she became very provocative in an argument they were having," the source added. "Things got out of control and he now says he wishes he just left the room.

"Normally Christian would just call a friend and go out to a pub to cool off," the source said. "But he was literally trapped into this confrontation with his mother and sister because there was an army of fans and paparazzi outside."

Bale, 34 - who is expected to attend the premiere of The Dark Knight in Barcelona on Wednesday - was arrested Tuesday after turning himself into police for questioning.

His attorney denied the assault claims, adding that the actor "left the station without any charge being made against him by the police."

His sister Sharon said Tuesday: "The police are dealing with it. It is an extremely sensitive situation. There is nothing more I can say."

Meanwhile, TMZ.com reports that the actor recently lost his cool on the set of Terminator 4 when the director of cinematography reportedly screwed up a shot.

The site claims he screamed "I will kick your a--," along with other profanities.

The actor also snapped at an Us Weekly reporter at the NYC premiere of The Dark Knight on July 14.

Asked if co-star Heath Ledger would nab an Oscar for his role as the Joker, Bale snipped, "Anybody's an a--hole, who would try to predict that," before walking off.

...He isn't very close with his Mother, and then she pulls this? Yeah, you can bet they won't be buddy buddy anytime soon.  And as for Bale, he's obviously not the nicest guy on the block... but everyone has an off day.  All this hooplah over the movie, and completely being overshadowed by Heath, may have gotten to him.  Lets hope he keeps his cool from here on out.