President Klaus of the Czech Republic is holding out on signing the Lisbon Treaty, despite both houses of the Czech Parliament ratifying it - the only other head of state to do so is President Lech Kaczyński of Poland. Klaus has even stated that he'll be the last person to sign it.
But EUobserver has reported that Czech MPs (from the CSSD party) are getting tired of Klaus' antics (and presumably also of the ceremonial president ignoring the will of parliament), and may draw up a motion to override the President so caretaker prime minister Jan Fischer can sign the Treaty and complete the ratification process in the Czech Republic. If there is a vote, it is likely to only take place after the Czech Constitutional Court has dealt with the latest Lisbon Treaty complaints (which may be September, or, if the case is thrown out, mid-July). The motion would only need a simple majority in both houses to pass, so it would be easier to get through than the Treaty itself, but there's no guarantee that the motion would have enough support. At the moment the CSSD are only debating the option.