Eclipse stuck while deploying to AppEngine

If Eclipse gets stuck in the middle of the deployment process open your command line and do this (in Ubuntu):

'.eclipse/org.eclipse.platform_WEIRD_NUMBERS/plugins/com.google.appengine.eclipse.sdkbundle_MORE_WEIRD_NUMBERS/appengine-java-sdk-VERSION/bin/appcfg.sh' rollback '/home/tom/PATH_TO_YOUR_PROJECT/war/'

Enter your mail address + password and you're good to go.