They aren't throwing flowers at us either. Something about us continuing to attack across their border with Afghanistan.
The latest screwup, and some idea of some possible blowback, is documented here at L.A.Times Online - and here's an interesting quote:
Such U.S. military operations are politically dangerous for Pakistan's president, Pervez Musharraf, a close ally in Washington's war on terrorism. Islamic parties, which form the main opposition in parliament and govern two provinces on the Afghan border, accuse Musharraf of being too willing to accommodate the United States. Islamic militants have made several attempts on Musharraf's life.If another attempt succeeds, or we succeed in destabilizing Pakistan enough so that our friendly dictator is overthrown, then the Islamic extremists are poised to take over - and doesn't Pakistan have nuclear weapons?