[fhawk]

edit /tmp/ispconfig3_install/install/lib/install.lib.php
find this:

if(stristr($content,'CentOS release 5.2 (Final)')) {
$distname = 'CentOS';
$distver = '5.2';
$distid = 'centos52';
$distbaseid = 'fedora';
swriteln("Operating System: CentOS 5.2 or compatible\n");
}

change it:

if(stristr($content,'CentOS release 5.3 (Final)')) {
$distname = 'CentOS';
$distver = '5.3';
$distid = 'centos52';
$distbaseid = 'fedora';
swriteln("Operating System: CentOS 5.3 or compatible\n");
}