Ouch! I feel your pain. Back in March of this year, I was in Tokyo and I bought the wonderful EF-S 10-22mm lens (with a Kenko protector filter) for my XT. I'd wanted a wide-angle lens for a while, and if there is any place on Earth that justifies it, it's Tokyo.
I bought the lens on a Thursday night, about 8PM in one of the electronics malls in Shinjuku. I shot perhaps 20-30 pics that night, just messing around. The next morning, at about 10AM, I was trying to get in an elevator to go to an observation floor in one of Tokyo's many many skyscrapers, and there was security checking everyones' bags on the way into the elevator. At the time, my XT and 10-22 were in a Tamrac holster-style bag over my left shoulder. I had to take the bag off my shoulder and place it on the table and open it for the security gaurd. After doing so, I THOUGHT that I re-shouldered the bag and headed toward the elevator. It was crowded and things were happening very fast, but all I remember was me yelling "ohh sh#t!!" and I bent over as fast as I could and caught the bag about 6 inches off the ground, but I was too late, as the slack in the strap was just enough to let the bottom, or lens portion of the holster if you will, strike the tile floor. I stood up quickly and was forced to proceed into the elevator. It was too crowded to open up the bag, so after what seemed like an eternity, when I finally got out of the elevator, I opened up the bag and pulled out the XT. I noticed that the very edge of the lens cap had turned white, the way plastic does when it gets bent. I thought, oh, that's not too bad. I took off the lens cap and millions of grains of white glass fell out and large chucks of glass hit the floor. Upon closer inspection there was a fine powder of white glass all over the camera body and inside the Tamrac bag.
I can't really describe how I felt other than to say that my guts churned to the point where I thought I was going to throw up and soil myself at the same time.
I was very lucky, as it turned out that all I had lost was the $50 Kenko filter. I took the XT and 10-22 to the Canon service center, which just happened to be a block away from my hotel, they checked out the lens and cleaned my camera and I bought a new filter and was on my way.
That feeling in my guts renewed my vigilance when it comes to securing my gear. Like I said, i feel your pain. Probably the best thing to do would be to have your 5D checked out by Canon, but it is supposed to be a very robust camera.
Good luck,
Michael