Ubuntu 9 fails to boot claiming a user permissions problem. cannot write file-- a hidden home directory file is not writeable

Would not boot into normal Gnome desktop as I would get a failure message instructing me to set user permissions. Couldn't get into grub single mode as the system didn't start with a standard grub menu, just proceeds to the boot up graphic.

Problem found and solution discovered: I switched to Gnome safe mode and finally got in. I changed the ownership of the users home directory which you can do by going to "cd /home" and ls -l to find the current ownership which had been taken over by clamav, apparently clamav, during it's last update, took possession of the users home directory (the directory which is in the home directory and has the same name you log on with) which caused the failure to boot. Whilst in the "/home" directory at the command line simply type chown username:username username and finally chmod 0755 username. You must be in the home directory this will change the owner and group to username and should solve the problem caused by the bad clamav installation. Username= the name you use to log on Ubuntu with.