Problem running on simple svn commands on CentOs

Hi there,

I'm driving crazy, trying to have SVN work properly on my CentOS server
(CentOS release 5.6 Final)

When installing subversion from the official CentOS repositories, I'm
getting version 1.6.11 with its mod_dav_svn.
Everything's ok 'till this point.

I then browse to my website's root directory and execute a shell script
which usually checked out and organize some source codes I wish to install.
(basically, I want to checkout out a whole CMS + some of its plugins, with
some mkdir and cd's directives to checkout the different source codes and
put them in the directories they have to be in)

The sh seems to execute quite well but 2 errors appear with no relevant
reason, when try to checkout 2 of my CMSs plugins :

svn: E155036: Please see the 'svn upgrade' command
svn: E155036: Working copy '/name_of_target_folder' is too old (format 10,
created by Subversion 1.6)

Seems that all my other instructions has been pretty executed, so I browse
to the target folder's parent directory, in which I first wanted to deploy
that so called "too old working copy" and then try to make a manual "svn
checkout" which results in ... Same error !

I then decide to try the 'svn upgrade' command, as suggested, which results
in : "upgrade" unknown command, ???? Ô_Ô

Then, tried to remove subversion 1.6.11 and got the source for the 1.7.5
version, which I did ./configure - make - make install and everything...

Second run with my shell :

* still the same errors on the same plugins
* no further "svn checkout" or "svn update" allowed without an "seems to be
part of subversion 1.7 or greater..." error
* svn upgrade still not working.

Sorry but I just touched the limit between my skills and the real life.

Can anyone help me with this issue please ?

thanks in advance for your answers (and by the way, forgive my english. I'm
French and did not practice your language for years ^^)

-- 
*Etienne.****
<http://www.musique2nuit.fr/>*