Okay, the only person who has suggested anything other than Kryptonite or virtual reality is Artemis, as far as I can see:

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As for the dust, hmmm. Old abandoned mine shafts near Las Vegas. EUREKA Area 51!!! Uranium! Atomic explosions! Little gray men! Stargate SG-1!.
I'm sure Artemis gets this better than me, but I'm thinking about those tests of A-bombs that the American military performed in the fifties somewhere in the deserts of Nevada. And Nevada isn't that far from Las Vegas, is it? Is it? (Ehhh... was geography my best subject at school? razz )

Anyway, providing Clark and Lois really have been driven somewhere where there might be some radioactive stuff in the ground, maybe Clark would react to it? After all, Kryptonite is radioactive. Maybe radioactivity in general interferes with Clark's powers, not just Kryptonite? (Okay, in the comics he was never really vulnerable to any other radiation than the Kryptonite kind, but hey, LnC isn't the comics.)

If the radiation is harming Clark, then maybe the metal of the truck was enough to shield him from the (probably relatively low-level) radiation outside.

Heh. I just had another weird thought, totally off on a tangent... but aren't we close to Roswell, too, you know, the mother and shrine of all UFO sightings? (Wouldn't bet on it, of course... frown for all I know Roswell may be in...um...Ohio?) Ah, but... just supposing that we are not too far away from it.... Wouldn't it be cool if those UFOs were slightly involved, too? Ah well, I'm just letting my keyboard do my chaotic mental blathering....

Ann