Our most recent release of Mantid, v3.9.0, contained some problems that were not highlighted during its usual beta testing period. We have put together a patch release to address these issues and we are pleased to announce that this is now available.
Installation packages can be found at http://download.mantidproject.org and the details of what is contained in the patch can be found at http://docs.mantidproject.org/v3.9.1/release/v3.9.1/index.html