Can't update system configuration

[Marcelo Magno T. Sales]

Hello,

I'm trying to change a file type association using System Settings -> File 
Associations. After I apply the change I want, I get a dialog which reads 
"Updating system configuration." with a progress bar that goes all the way to 
100% and then goes back to 0% and repeats this indefinitely. I can wait for 
days and it does not finish. If I cancel, the change is not applied.
This also happens when I try to make changes in the K Menu.
Any idea on what may be causing this problem and how can I solve it?

Thanks,

Marcelo