SOLVED :
This Thread is now closed having found ALL solutions for my problems...
For cliomail users experimenting problems with skin responding error 500...
Check in /ca/config.html your :
|?CA_PHP=/path/to/php5/|
In my case, i had to switch :
|?CA_PHP=/usr/local/php5/bin/php-cgi|
to
|?CA_PHP=/usr/local/php5/bin/php|
to make Skin work...
So To conclude, with this product CustomBuild, i'd say it's a good idea, but absolutely not user nor newbie admin level oriented...
After using, lots of tweeking is necessary to solve problems...