I'm not a gnome user, but I know there is a gconf-editor utility that can be used to set file permissions. Maybe your home directory permissions are screwed up.
Have look here:
openSUSE Tutorials
Enable the Advanced File Permissions Dialog in Nautilus | Tombuntu
I found this gnome
tutorial. Have a look at 'pitfalls' section towards bottom of page. Specifically, there is some info concerning what to do if everything seems messed up for a user. I would make sure you back up any crucial data (on usb stick) before attempting anything radical though.
Good luck.