AND FROM OUR BELIEVE IT OR DON'T DEPT.: When we reported last year that Poland's leading rock band, Lady Pank, had signed an endorsement deal with Fender guitars, we knew it was only a matter of time before all those capitalist luxuries would go to the band's head. Sure enough, the group's leader, Jan Borysewicz, was arrested after band members showed up intoxicated and began shouting obscenities on stage at a children's day concert last week in Wroclaw, Poland. According to PAP, the country's official news agency, police were called in after Borysewicz "used vulgar language while disrobing in public" before some 15,000 children and their parents in the city's Olympic Stadium yesterday. To make matters worse, the Wroclaw youth organization that sponsored the event petitioned the Ministry of Culture to disband the group for its "irresponsible conduct," the agency added.