I had the same error.
I have two user
When i log in with root username,i have this error.
But when i log in with oracle username,everything works fine.
After having problem i googled it and i wrote from terminal as recommended in here;
In my case;
--I logged in with root username and did write following commands in terminal
chmod 644 /home/username/.dmrc
chmod 755 /home/oracle
--I do not know if any wrong step i took while writing these commands from
--On the other hand when i try to find /.dmrc file i could not find it out.
---There is a file named oracle in my home path. I checked sub-folders. How can i exactly where it is?