[Ubuntu] How to fix the unmet dependencies for grass-gui ?

[Luís de Sousa]

Dear all,

I have the ubuntugis-unstable PPA registered in my sources.list
(Ubuntu 14.04). Two days ago an automatic system update tried to
install the new grass 7 meta-package, which failed due to unmet
dependencies. Right now I have different versions of grass-core and
grass-gui installed and grass fails to start.

Apt reports the following:

$ sudo apt-get build-dep grass-gui
Reading package lists... Done
Building dependency tree
Reading state information... Done
Picking 'grass' as source package instead of 'grass-gui'
Note, selecting 'libtiff5-dev' instead of 'libtiff-dev'
The following packages have unmet dependencies.
 libcairo2-dev : Depends: libcairo2 (= 1.13.0~20140204-0ubuntu1) but
1.13.0~20140204-0ubuntu1.1 is to be installed
                 Depends: libcairo-gobject2 (=
1.13.0~20140204-0ubuntu1) but 1.13.0~20140204-0ubuntu1.1 is to be
installed
                 Depends: libfontconfig1-dev (>= 2.2.95) but it is not
going to be installed
                 Depends: libglib2.0-dev but it is not going to be installed
 libproj-dev : Depends: libproj0 (= 4.8.0-2ubuntu2) but 4.8.0-4~saucy2
is to be installed
E: Build-dependencies for grass-gui could not be satisfied.

I have tried the basic tricks in the book to fix these dependencies:
install -f, autoclean, etc, to no avail. The following step would be
to remove the PPA altogether, which obviously I can not do because I
need grass.

Could I get these dependencies from a different PPA? Otherwise, would
there be any other way of getting grass running again? I do not mind
continuing to use grass 6.4.

Thank you,

Luís