If my reminds are correct, my first version of gtk had been installed during the installation of my Linux in the /usr/ directory.
I installed the newer version (so 2.2.4 in your case, 2.4.2 in mine) in the /usr/local directory (which is the default directory when installing from sources), so there was a conflict between the older version in /usr/ and my new version in /usr/local.
So I simply reinstalled the new version in the /usr/ directory so that the older version was erplaced. To do so, simply write "./configure --prefix=/usr/" in order to install in the /usr/ directory instead of the default directory. The do "make" and "make install"...
Instead of installing from the sources, you can also find the rpm file for your distrib. This will automatically install the whole stuff in the convenient directories.
Note : When installing programs from sources, it's preferable to install them in the /usr/local directory (usually the default one for the installation). But for libraries like gtk, or any other libraries used by your different programs, which are sometimes automatically install with your Linux, prefer to choose the /usr/ directory, especially when there already is an older version installed.