WASHINGTON (AP) - An experimental interceptor missile failed to get off the ground in a test of the U.S. national missile defense system early Wednesday, raising new doubts about prospects for the imminent activation of the system. In the test, a target missile, a simulated ICBM with a mock warhead, was launched without problem from Kodiak, Alaska, at 12:45 a.m. EST, a statement from the Defense Department's Missile Defense Agency said. However, 16 minutes later, an "unknown anomaly" led to an automatic shutdown of the interceptor missile shortly before it was to launch from the Ronald Reagan Test Site at...