I don't really know ISPconfig but I assume there is some kind of vhost template you can edit? I can really recommend using this on your hosting...
Yes we do! http://www.howtoforge.com/putting-varnish-in-front-of-apache-on-ubuntu-debian ;)
What videocard are you using? You might want to install the drivers for it. Are they installed? Check Hardware Drivers for that. Otherwise...
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