MEMRI has posted a translation of an interview with Osama bin Laden’s former bodyguard, Nasser Al-Bahri. He confirms what we already knew; theological differences do not preclude cooperation between the Sunni al Qaeda and Shiite Iran. Al-Bahri explains (emphasis added):

Nasser Al-Bahri, as seen on Al-Arabiya TV on May 4, 2007.
Al-Bahri’s interview was published at the same time as we learn that Iran has been caught “red-handed” delivering explosives to the al Qaeda-affiliated, Sunni Taliban in Afghanistan. But none of this is terribly new. (See, for example, here, here, here, and here for starters.) Some counterterrorism analysts think that theological differences are everything in these matters. They are not. The pattern of Iran’s support for Sunni terrorists the world over should have been clear years ago. As long as the terrorist forces are targeting Iran’s enemies, and especially Tehran’s main enemy–the United States–the Shiite-Sunni divide is easily bridged. The real question is this: what is America’s policy for dealing with this well-substantiated pattern of cooperation? As far as I can tell there is none.