Chris,
Sorry that you are seeing this issue.
Can you please check if you can get the Mylyn Mantis connectors to work on Eclipse Kepler (4.3.1) which is the base version of MyEclipse 2014 ?
We do not provide intrinsic support for third party plugins, but we will try to assist you in this case. Please let us know how it works on Eclipse Kepler to help us investigate the issue with MyEclipse.