Tomcat Manager won't undeploy

[Mark]

I'm using Tomcat 4.1.12 and can't get the manager 'undeploy' command to work. Other mgr commands such as stop, start, remove, list, etc. work, but not undeploy. The application is defined in server.xml with context path="/myapp" docBase="myapp" and lives under webapps/myapp. Using this manager command:
http://localhost:8080/manager/undeploy?path=/myapp

I get the following simple response:
FAIL - Cannot remove document base for path /myapp

and the Tomcat log shows:
2002-12-02 10:09:37 Manager: undeploy: Undeploying web application at '/myapp'

Anyone know what the problem is? I stopped the app first but that doesn't help. I searched the archives to no avail. I'm looking at integrating TC manager functions into our Ant build for a complete clean build/redeploy, but have hit a wall here.

Thanks in advance.
Mark