问题：The connection to adb is down, and a severe error has occured.
You must restart adb and Eclipse.
Please ensure that adb is correctly located at ‘D:\android-sdk\platform-tools\adb.exe‘ and can be executed.
尝试：手动双击起动D:\android-sdk\platform-tools\adb.exe，在任务管理器里面闪一下马上消失，手动启动失败。。
解决：发现任务管理器中有一个androidadb，不知道是什么，杀死此进程；重启eclipse，看到adb进程正常启动，然后正常调试，问题解决。。