The Iron Curtain's been down for some time, but the diplomatic love-in underway between Russia and the United States is enough to make a seasoned diplomatic blush. Both sides seem ready to agree that the ABM Treaty is easy to fix, Missile Defense, Pahjhalstah! Economic troubles? Nothing a little debt relief can't fix. And NATO? Sign on the dotted line. Although the speed with which Presidents Bush and Putin are scraping away the remaining frost of the Cold War is dizzying to watch, there are those saying that none of this will be a walk in Gorky Park, and that once the nations get past their mutual desire to stamp out terrorism, old suspicions, pride and the problems will be back.