This story:
http://www.breitbart.com/news/2006/04/19/D8H34DGG0.html, says:
A radio problem on the Marine One helicopter prevented it from taking off from the White House lawn Wednesday, forcing President Bush to wait for a motorcade to take him to nearby Andrews Air Force Base.
Bush and his senior advisers had boarded the helicopter and it revved up in preparation for takeoff, but after about a minute its engines were shut down. Bush got off smiling.
"We had an issue with the helicopter," the president said. "Everyone's safe."
Bush walked off to shake hands with visitors who came to see the takeoff. White House Deputy Chief of Staff Joe Hagin said the helicopter's radio had failed. "They couldn't talk to anyone," he said.
A motorcade was being assembled to take Bush to the air force base to begin his flight to Tuskegee, Ala.
This sounds rather fishy to me. As I recall from when I was piloting a few years ago, any IFR-rated aircraft has to have dual navcoms. It is not plausible that Marine One does not carry full IFR equipment. Therefore, even if a radio was out, they'd still be able to talk on the second radio. Not, "They couldn't talk to anyone", as we're being told.
I'd guess there was some other issue that they don't want to talk about. Since we're fighting a war and they have need from time-to-time to not tell us everything, I guess I can accept this may be one of those times, so I'll wish them good luck and Godspeed. Still, I do wonder what was up...