Two things:

First, apparently the numbers are wrong. The IAEA found three tons in January 2003, but the Iraqis reported 141 tons (just this month) because that was what was on a 2002 declaration.

And then, of course, we've got Bill Gertz's story. Basically, the impression I get is that, in the run-up to the war, the Russians decided to take back things they'd given to Saddam that they shouldn't have.