Chernobyl disaster: long-term global damage?

A freind of mine claims that contamination from the Chernobyl disaster has done significant damage to Russia’s grain-producing lands. I’ve also heard of a “radiation cloud that went round the earth” and similar claims of long-term widespread, even global, contamination.

Anyone got the straight dope on this? I know the area immediatly around the Chernobyl plant is uninhabitable. I don’t know how far it goes, or how bad it is a few hundred miles or more downwind.

Kiddofspeed’s - Ghost town gives an interesting insight into the local effects of Chernobyl.