Try the following:
Close Eclipse.
Restart your phone.
End adb.exe process in Task Manager (Windows). In Mac, force close in Activity Monitor.
Issue kill and start command in platform-tools
C:sdkplatform-tools>adb kill-server
C:sdkplatform-tools>adb start-server
If it says something like ‘started successfully’, you are good.
For anyone using OSX (I’m aware OP isn’t):
What worked for me in the end was removing the android settings folder in the home directory.
rm -Rf ~/.android