Try the below steps:
- Close Eclipse if running
- Go to the Android SDK platform-tools directory in the command prompt
- Type
adb kill-server
(Eclipse should be closed before issuing these commands) - Then type
adb start-server
- No error message is thrown while starting the ADB server, then ADB is started successfully.
- Now you can start Eclipse again.
It worked for me this way.
Restart your phone as well!