I've installed youtrack for windows (.exe) and started to use it. After some time i had to reboot my webserver and... After reboot it lost its database and displayed start page with license agreement and root password. I tried to restore it but no luck here - when I start "YouTrack Web Server" issues again is empty. WTF???
Here's how I restored database: http://confluence.jetbrains.net/display/YTD2/Restoring+Database+from+a+Backup