Go back to the 'Configure the webserver' step, part 4, right click on the virtual directory 'cognos10' previously created, choose properties and tick all the following box's:
After clicking OK, complete the 'Update the Cognos Configuration' steps. Then proceed through the steps in 'Setup of Cognos connection to datamarts using ORACLE' and once complete, undo the changes made to the properties by going back to the cognos10 properties and only have the following box's ticked:
Recomplete the 'Update the Cognos Configuration' steps.