A newer version of dev-java/jaxen was released (see bug #95755). That version introduces a new dependency on dev-java/xom. Since xom has no sparc keyword I had to drop the ~sparc keyword. Please test and keyword dev-java/xom and afterwards feel free to readd your keyword to the newer jaxen version. Thanks in advance.
~sparc keywords added to xom and jaxen-1.1_beta6. Thanks for the bug report :)