Ok. It appears to be back again. I did a complete uninstall of DOA (Windows 7 x32) it was present under the programs list as DOA for XE and DOA for XE. Uninstalled both.
Started XE2.Checked it was not in the list of packages for XE2. Shut down XE2.
Did clean install. Checked on the packages list, it's there as Direct Oracle Access 4.1.3, but not checked. I've got no projects open and if I check it then I get the message again that it "...can't be installed because it was created with a different version of Delphi or CBuilder".
Not sure how I managed to get a build of my program after doing a clean, but it did, once.