These are the packages that would be merged, in order:
Calculating world dependencies /
!!! Multiple versions within a single package slot have been
!!! pulled into the dependency graph:
('installed', '/', 'sys-apps/hal-0.5.8.1', 'nomerge') pulled in by
('installed', '/', 'gnome-base/gnome-mount-0.5', 'nomerge')
('ebuild', '/', 'sys-apps/hal-0.5.7.1-r3', 'merge') pulled in by
('ebuild', '/', 'gnome-base/gnome-vfs-2.18.0.1', 'merge')
It may be possible to solve this problem by using package.mask to
prevent one of those packages from being selected. However, it is also
possible that conflicting dependencies exist such that they are
impossible to satisfy simultaneously. If such a conflict exists in the
dependencies of two different packages, then those packages can not be
installed simultaneously.