My story:
Installed in September Ubuntu 10.04 x64, and created a new empty home folder for my user. All was fine, but approximately in the middle of October Nautilus began to work very slowly. When i click on folder - I can wait from 4 up to 30 seconds... Nautilus shows white background and just is trying to load information. And my CPU's are beginning to work on full power and about 200mb of system memory is used. Nothing was done with system before this bug appeared. So, in previous versions of nautilus all was fine. Although I noticed, that if I temporary rename my home folder and create just a new empty one and log in - nautilus works perfectly. So, something is overloaded in /home/user/ dir, but i don't know what. Cleaning of .thumbnails didn't work for me

Are you sure you're not running out of space? du -h or Disk Usage Analyser.

yes I am. i have 18Gb of free space.

Well, running top might give you an idea of which processes are using up your CPU.
You could also try typing nautilus in a terminal, and seeing if you get a swag of error messages.
And you could try
, and then log out or reboot.

I used Top before writing here. All is ok, and when i start nautilus - it uses my CPU.
I although tried Nautilus in terminal - but it gave me no error messages
Moving .config dir helped me, thanks. Now nautilus works faster and doesn't use all my CPU's power.
But it is undoubtedly bug of new nautilus, because previous versions didn't have such problem.