President Obama, in his recent offer to the Russians, appeared to propose abandoning the missile defense system that the previous administration wished to install in Poland and the Czech Republic. The quid pro quo was Russian support for keeping Iran from obtaining the missiles that the system was designed to stop.
The Russians are highly unlikely to help out with Iranian missiles, especially as it was they who sold Iran the missile technology in the first place. Obama, in a further unnecessary weakening of the U.S. position, implied that he might abandon the missile defense system anyway, since it represented 'unproven technology'.
So where did that leave the Czechs and Poles? With both feet firmly planted in midair, wondering if once again they'd been sold out by a great power. The Czech parliament has yet to approve the deal (the prime minister had to delay the vote for fear it wouldn't pass). And the Polish Foreign Minister has just wondered out loud whether his country will regret trusting the United States.
If you can stand to read the details, this editorial from Investor's Business Daily kinda sums up the problem.