jaxb from the experimental overlay depends on istack-commons-tools-2007* and will not work the istack-commons-tools-2009* that is now in portage. Since the 2009 version in portage is unmasked, it will get installed instead of the 2007 version producing an error during the jaxb-2.1.10 install.
Also, the istack-commons-runtime dep should be updated as well. Bug #275049 may be of interest.
[java-experimental] is gone. Closing.