open the terminal and type
sudo find / -name .DS_Store -exec rm {} \;
it will ask you for your password, type your password, it will look like you are typing nothing but you are. hit return and wait a minute or 2.
I posted the thread about os x and global preferences. I have used this command and have had no problems since. One thing though. If this does not work. you may need to do a system file check and then run the command. Don't ask me why, but the commands worked fine on my 2 imacs and then I went to my ibook and it didn't work. I tried it several times and finally ran a file system check, although nothing appeared to be wrong as soon as I typed the command the next time it worked.