I still see the error with todays snapshot of JBoss 7.1.0.Final.
Attached is a reworked version of my JSR88 deployer. To reproduce the problem:
1) unzip to your eclipse workspace
2) import as "existing project"
3) fix the build path, if your JBoss 7.1 is not at "C:\temp\jboss-as-7.1.0.Final-SNAPSHOT"
4) open "build.xml" with the Eclipse ant file editor
5) run the task "deploy.j2ee.ear"
This will deploy the war file "StrutsBasics.war" (included in the project) to your local JBoss (localhost, port 9999). Now you should see the "scratchDir" error message in the server console.
To verify that the app does not work: this URL will fail: http://localhost:8080/StrutsBasics/geometricmodel.jsp