On some x86-64 systems the openssl code shipped in install_ispconfig/compile_aps doesn't compile. ISPConfig Installation fails saying something about shipped PHP not working, the first ERROR in the log being some register thing on openssl. To fix this, edit install_ispconfig/compile_aps/compile and look for a line like Code: ./config --prefix=${INSTALL_ROOT/openssl || error and change it to Code: ./Configure linux-generic64 --prefix=${INSTALL_ROOT/openssl || error I am not familiar with your ticketing system and to be honest I am busy and don't want to spend time on learning it. Anybody who reports this fix/workaround to the developers is welcome to take all the credit.
Thanks for the report. The forum is the right place to report errors in ISPConfig. I added it to the developers Bugtracker.
On which distribution did you have that problem? I've just tested on Debian Etch AMD64 and had no problems installing ISPConfig.