Today I got fed up with this, stopped everything and recompiled a lot of packages.
first upgraded to gcc-3.4.5 and changed locale to use iso8859-1, gdm was changing to UTF-8 at the X init process and I didn't realize about that. Also I've switched to ck-sources.
and reemerged...
>>> x11-base/xorg-x11-6.8.2-r6
>>> media-libs/libpng-1.2.8-r1
>>> media-libs/jpeg-6b-r6
>>> media-libs/tiff-3.7.4
>>> sys-devel/gettext-0.14.5
>>> media-libs/freetype-2.1.10
>>> sys-libs/zlib-1.2.3
>>> dev-libs/glib-2.8.5
>>> x11-libs/pango-1.10.2
>>> dev-libs/atk-1.10.3
>>> x11-libs/cairo-1.0.2
>>> x11-libs/gtk+-2.8.9
>>> x11-themes/gtk-engines-2.7.1
>>> x11-libs/wxGTK-2.6.2-r1
>>> net-p2p/amule-cvs-3
Added support for tiff in gtk+, wich before was missing.
And finally rebooted the computer.
Then... boila! wxGTk && aMule worked fine again!
I really don't know were was the problem! ...since the 2.1.0 release I've been recompiling glib gtk+ gtk-engines wxGTK and aMule again and again trying different versions and testing new thinks and nothing worked.
But, well, now it's solved, so I'll assume this was a strange behaviour of my system. I'll add and "invalid" tag to the title of the post.
Thanks for the help.