Please make sure you installed:
1) Eclipse Indigo SR2 for Linux: http://www.eclipse.org/downloads/download.php?file=/technology/epp/downloads/release/indigo/SR2/eclipse-jee-indigo-SR2-linux-gtk.tar.gz
2) Plugin in from the installation, the path like: Oracle/Middleware/ocep_11.1/eclipse-update-site/cep-tools=18.104.22.16830109-2314/. Note the plugin download site is not updated. So you can't use the install Plugin via URL
I assume you are using PS6. For other version, please check the document accordingly.
I have installed Eclipse Helios on Windows 7 32-bit. I am getting the same error on attempting to create my first CEP application: The location "C:/Oracle/Middleware/ocep_11.1" contains the BEA home definition file "C:/Oracle/Middleware/ocep_11.1/registry.xml," but that file does not contain an Oracle CEP component entry with an "InstallDir" attribute. Does anyone have the solution to the problem?