I am running that setup on Centos 5.4.
I have the following issues:
1) When I create sites on the slave server (using of course the ISPConfig interface on the master), I noticed that the Allow Override and PHP open_basedir fields on the Options tab are empty for those sites.
2) I created those sites on the slave as subdomain2.domain.com and subdomain3.domain.com. If I go to http://subdomain2.domain.com
, it accesses the content of subdomain1.domain.com which is a site created on the master server. In fact any subdomains.domain.com created on the slave server access the contents of subdomain1.domain.com.