When we have a user who wants to use our Extended Analytics feature to connect to an Oracle database, we tell them to install the Oracle OLE DB DLLs.
Some of the DLLs that are installed by these two processes in the two different directories have the same name and are, in theory, the same DLL. However, there is no guarantee that the user has selected the right version of the Oracle OLE DB DLLs to install on his server machine, where -- in this case -- "right" can be translated as "the same version as were installed for Essbase integration".
If you run the Essbase integration, everything works.
If you run Extended Analytics, everything works.
If you run them both, hilarity ensues, at least if you have not managed to successfully match the DLL versions between the two installs.