Looking at the file on my system it shows with -rw------- permissions, ie 600 in octal language, not 644, but I don't think that would make any difference when trying the chmod command.
Try renaming the file from Ctrl+Alt+F1 command line with
which is one answer I have seen mentioned before many times.
sudo mv /home/user/.ICEauthority /home/user/.ICEauthorityOLD
Just out of interest, have you made use of sudo to start graphical applications instead of gksu or gksudo, as that can cause this problem. Srr Root-sudo in my signature for details and explanation of what you should always do.