You're on a 64-bit system which is not supported officially yet. You have to tweak the installer a little bit:
http://www.howtoforge.com/forums/showthread.php?t=127
http://www.howtoforge.com/forums/showthread.php?t=286
Before you try to install again, you should restore your old working ISPConfig. There are backups of /root/ispconfig and /home/admispconfig and also an SQL dump of the database in /tmp.