Our builds are configured to execute sonar with the Sonar plugin. This occurs after the initial reactor's build cycle completes, so all of the artifacts from the build have been installed to the local repo. On executing a release, the release performs as desired, but sonar executes after it is finished (as part of the jenkins build, but a separate reactor) with the new versions in the poms after the release. It fails because it cannot find the dependencies, because they have not been build/installed yet.
Current work-around is to disable sonar for the release, execute release, enable sonar, run another build.