page always show Loading when use gwt dev mode by use gwt-maven-plugin

try to use gwt-maven-plugin to start gwt dev mode thru "mvn gwt:run" for kie-wb-webapp module, and successfully start it up and got the GWT dev mode GUI. But when loading the page, always got "loading application" and no other respond.

the "mvn gwt:run" output as below:
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building KIE Workbench - Webapp 6.1.0.CR1
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] >>> gwt-maven-plugin:2.5.1:run (default-cli) @ kie-wb-webapp >>>
[INFO]
[INFO] — maven-enforcer-plugin:1.2:enforce (default) @ kie-wb-webapp —
[INFO]
[INFO] — maven-enforcer-plugin:1.2:enforce (enforce-java-version) @ kie-wb-webapp —
[INFO]
[INFO] — maven-enforcer-plugin:1.2:enforce (enforce-maven-version) @ kie-wb-webapp —
[INFO]
[INFO] — maven-enforcer-plugin:1.2:enforce (enforce-plugin-versions) @ kie-wb-webapp —
[INFO]
[INFO] — build-helper-maven-plugin:1.7:parse-version (default) @ kie-wb-webapp —
[INFO]
[INFO] — maven-enforcer-plugin:1.2:enforce (no-managed-deps) @ kie-wb-webapp —
[INFO]
[INFO] — buildnumber-maven-plugin:1.2:create-timestamp (get-build-timestamp) @ kie-wb-webapp —
[INFO]
[INFO] — buildnumber-maven-plugin:1.2:create (get-scm-revision) @ kie-wb-webapp —
[INFO] Checking for local modifications: skipped.
[INFO] Updating project files from SCM: skipped.
[INFO] Executing: /bin/sh -c cd /home/gli/workspaces/java/git/opensource/droolsjbpm/kie-wb-distributions/kie-wb/kie-wb-webapp && git rev-parse --verify HEAD
[INFO] Working directory: /home/gli/workspaces/java/git/opensource/droolsjbpm/kie-wb-distributions/kie-wb/kie-wb-webapp
[INFO] Storing buildNumber: 8f06ce124f0b8521c33c16b4b509799f5b69cdb3 at timestamp: 1403760963279
[INFO] Executing: /bin/sh -c cd /home/gli/workspaces/java/git/opensource/droolsjbpm/kie-wb-distributions/kie-wb/kie-wb-webapp && git rev-parse --verify HEAD
[INFO] Working directory: /home/gli/workspaces/java/git/opensource/droolsjbpm/kie-wb-distributions/kie-wb/kie-wb-webapp
[INFO] Storing buildScmBranch: UNKNOWN
[INFO]
[INFO] — maven-resources-plugin:2.6:resources (default-resources) @ kie-wb-webapp —
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Copying 22 resources
[INFO] Copying 126 resources
[INFO]
[INFO] — gwt-maven-plugin:2.5.1:resources (gwt-compile) @ kie-wb-webapp —
[INFO] 17 source files from GWT module org.kie.workbench.FastCompiledKIEWebapp
[INFO]
[INFO] — maven-compiler-plugin:2.5.1:compile (default-compile) @ kie-wb-webapp —
[INFO] Nothing to compile - all classes are up to date
[INFO]
[INFO] <<< gwt-maven-plugin:2.5.1:run (default-cli) @ kie-wb-webapp <<<
[INFO]
[INFO] — gwt-maven-plugin:2.5.1:run (default-cli) @ kie-wb-webapp —
[INFO] create exploded Jetty webapp in /home/gli/workspaces/java/git/opensource/droolsjbpm/kie-wb-distributions/kie-wb/kie-wb-webapp/target/kie-wb-webapp-6.1.0.CR1
[WARNING] Your POM <build><outputdirectory> does not match your hosted webapp WEB-INF/classes folder for GWT Hosted browser to see your classes.
[INFO] 2014-06-26 13:36:30,941 [main] WARN Environment variable M2_HOME is not set
[INFO] Created new window in existing browser session.

And GWT Dev Mode GUI as attachment show

The page loading result see attachment too