How many times have you heard this? Well, I don't believe he lied. At worst, he and his administration became over-concerned (not a good thing either, but not a lie) about the prospect of Iraqi WMD after Sep 11. However, according to the Portuguese PM President Clinton was convinced that Saddam had WMD right up to the fall of Saddam's regime last April.
This can be read in two ways. One, President Clinton is acting Presidential and backing up the current holder of the office. Or, two, he is cutting the rug under Howard Dean by basically saying that it was not unreasonable for President Bush to believe Saddam had such weapons. This would help (a) Wesley Clark - thought to be the Clintons' choice and (b) Hillary, whose 2008 ambitions will presumably go up in smoke if Dean is elected this year.
{Link found through Instapundit.}