Today I was chatting with my friend using Yahoo Messenger. I logged out due to some reasons and when I tried to logged in again it was showing a window "There was a problem signing into yahoo Messenger! Please try a bit later New User, Sign In Problems, try again". I tried two or three times, No Success 
Then I thought of logging into yahoo mail, It was saying that "Invalid ID or password.Please try again."
I tried with my wife's yahoo id and it is working fine without any issues.
I thought of Hacking, Caps lock etc. I planed to recover the password using forgot password
It is asking for two things
1. My Yahoo Id
2. Verify your identity with a previously-used credit card
entered both the information and clicked "Continue". Then it came with an error message "FEATURE_ERROR_USER_OPEN_NO_ACCESS", What's That ?
Had a search using Google and one solution found was to use http://yahoo.co.in but in my case that also failed.
Then I searched again and what I understood is that Yahoo is doing something like migrating accounts or something like that. It will be ok after some times. So waiting for that. Still, after 30 min no Joy 
Then I tried to login to the messenger using http://webmessenger.yahoo.com/ Yes, Yes, it worked !!!!!! am happy to know that my id is not hacked 
The error "FEATURE_ERROR_USER_OPEN_NO_ACCESS" means
FEATURE_ERROR - the feature from Yahoo! which you are trying to use for that particular ID is unavailable
USER_OPEN_NO_ACCESS - the user ID which you are trying to reset the password cannot be opened for recovery, currently you cannot be allowed access to the specified user ID
Edit:-
Am able to login now, after 3-4 hours
So Dont be panic 
You will be able to login after sometime. Wait that is the only thing you can do