Sorry, you're not giving too much information ... What happened? What did you do? Which version of Geeklog?
To restore a backup, drop your old database and import the backup, either with phpMyAdmin (you might run into timeouts there, depending on how big the backup is) or from the command line:
mysql -uusername -ppassword -Ddatabase_name < i>your_backup.sql
bye, Dirk