A recent update updated lot of packages on Centos 5. Then next update try to replace x86_64 libs by i686 libs with lot of unresolved dependencies.
yum check-update gives:
Obsoleting Packages tdelibs.i686 3.5.13-9.el6.opt trinity-3.5.13-el5 trinity-kdelibs.x86_64 3.5.13-8.el5.opt installed tdelibs-devel.i686 3.5.13-9.el6.opt trinity-3.5.13-el5 trinity-kdelibs-devel.x86_64 3.5.13-8.el5.opt installed
Fortunately, installing tdelibs.x86_64 solves the problem.