I'm running Hudson 1.160, version 0.8.4 of the Cobertura Plugin and Cobertura 1.9.

Everything was working fine until we started using the JiBX Object mapper.
After that, Hudson complains that the build failed even though it was
successful, the unit tests passed, and the Cobertura graph is updated. On
subsequent builds, Hudson sends out and email that the build is now back to
normal, but the server still says that the build failed without any evidence why.

Some of these problems make sense – both JiBX and Cobertura instrument the
classes. But this works fine on the command-line.

I'm going to attach a snippet from the coverage.xml file that has the JiBX
instrumented classes to see if that help you. If you need more info, let me know.