After a botched install of a .ear file to my Oracle 9i application server, subsequent attempts to uninstall the application failed with the above error. Google was of no help; Metalink listed the problem, but offered no workaround. Although it would have been possible to just "get on with it" and use a different name, having a broken application listed among my installed applications was just too ugly.

Fortunately, I was able to remove the broken application by taking the following steps:

1. I stopped the OC4J_home instance where my application was installed.
2. I located the application's installation files. In my case, they were at

   C:\ora9ias\j2ee\home\application-deployments\application-name\
   C:\ora9ias\j2ee\home\applications\application-name\
   C:\ora9ias\j2ee\home\applications\application-name.ear

   I removed these files and directories.
3. I edited C:\ora9ias\j2ee\home\config\default-web-site.xml, removing from it the line corresponding to my application. Needless to say, I made a backup copy first.
4. I also removed the line corresponding to my application from C:\ora9ias\j2ee\home\config\server.xml.
5. I restarted OC4J_home.