1) Did you ever alter anything in the ispconfig database scheme since you installed ispconfig, e.g. added a table in the database or added column in one of the tables? This might cause a problem when the ispconfig installer tries to load the dump of the old database into the new database scheme.
2) Restore the ispconfig mysql database, there should be a backup in the /root folder.
2) Check that the the file /usr/local/ispconfig/server/lib/config.inc.php contains the correct login details for the ispconfig mysql user
If 2) no, and you have backup of that file, restore it. If you dont have a backup, we will restore it from the template.
If 2) yes, try to update to ispconfig 126.96.36.199 first, by downloading ispconfig 188.8.131.52 tar.gz file, unpack it and run the update.php script in the install directory.