DDms is not opened sometimes

In my system sometimes ddms (dalvik debugger) tool sometimes doesn't open. What is the problem? And what can I do for this problem? When I open it through command prompt it displays the following error:

38:16 E/DeviceMonitor: Failed to read the adb response!

38:24 E/DeviceMonitor: Failed t开发者_运维问答o read the adb response!

What can I do?

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Sometimes I get problems attaching the debugger to a device. Running this from the command line can fix it.

adb kill-server
adb start-server

Also, running more than one version of Eclipse (or Eclipse plus the DDMS tool itself) can result in problems (you get warnings about this now I believe).