Ubuntu 11.10 enforces gThumb for even normal non-image file browsing. gthumb might be a good image browser but its a pathetic file browser (compared to nautilus) can we get nautilus back in 11.10 ?
I have just found a solution here:
Go to the end of the article and you will find the easiest way to do it as follows:
One more way - for "mousemonkeys", like me Just do in terminal exo-preferred-applications then switch to Utilities tab and select File Manager you prefer. And that's all!
You could need to install exo-utils before, but it will prompt you if necessary. Anyway the command to install it is:
sudo apt-get install exo-utils