Suddenly, no file associations in Gnome/Nautilus

Hi,

I have a strange problem: suddenly, in Nautilus and in Gnome (Fedora 7
with all updates) the file associations are no longer working.

If I open a Nautilus windows in a folder where are present different
document types (images, pdf, openoffice), all the icons are of the
generic file type and no program is associated. So, if I double-click on
odt (openoffice document file) file, I get a warning window:

Couldn't display nomefile.odt

And in the properties of the file, no application is associated. This
for ALL file types :(

This behavior is related to all normal users of the computer. Instead,
under the root account all associations work properly.

Some hint ?

Andrea