I cannot access into yahoo chat rooms and after login to yahoo messenger it says that social plugin and music plugin error and even i cannot install any plugin, it says plugin cannot be installed.

Dear Friend.. My suggestion is that . check the yahoo messenger setting . some plugin may be not installed correctly, thats y you are facing the given problem...

This is cause by some plugin error.
may be you can not see messages even after reinstalling yahoo messenger.
so...here is the easy way to solve this problem.

1- create a "NEW USER ACCOUNT" from 'control panel>user account for yourself and restart your computer.
2- login to the new user account and go to control panel> user accounts, and then delete ur old user account ( u may want to save your personal folder and files when prompt)( if you want to save your internet explorer favourites , do it manually )
3- just connect your internet and enjoy yahoo messenger.

how do it fix the socialview errors

double click icon of yahoo messenger you will see sign id and password type there click signin

Uninstall everything yahoo related from add/remove programs. Go to your C:, then Program Files and delete the yahoo folder from there also. Now go download ccleaner from www.download.com and run the cleaner, once that is done run the registry cleaner a couple times.

Try re-installing the latest yahoo from there. IF that failed also, you have one last shot that will work but it can be tedious a bit and a little dangerous so make sure to back up your files before proceeding. If the error still happens, do all of the above except for re-installing the yahoo. Now from the run command (Windows Logo Key + R), type: regedit <Hit ENTER>. Up top click on Edit and then click Find. Type: Yahoo! <Hit Enter>. Delete what it found and then press F3 to find the next yahoo! item. Delete everything it finds till there are no more matches found. Close the Regedit and reboot the pc. Now re-install the latest Yahoo Messenger and the problem is gone. I have done this several times for clients and this fixes it 100% of the time. Cheers!

Perhaps you are a fresh member of yahoo. that's why you cannot see a members of yahoo if they are online.
NOTE! But if you want to have add friends bro, you can enter on yahoo chat room and socialize with them. OK follow this steps, how to get in. 1. click messenger. 2. click yahoo! chat. 3. Then select join room. 4. Select what type of category you want to join. 5. Then Choose a room you want to socialize. 6. wait for the loading bar when it's done then click enter. 7. type the verification letter posted at the top of your text box. 8. your done! you can now socialize and add some friends. God Speed and God Speed.

I assume that you have downloaded Yahoo messenger and you have login account.
In order to chat to an individual you need to know the persons yahoo id. If you know it then go to CONTACTS/ADD A CONTACT.
By doing so, an invitation will be sent to the person and once the person is online and agrees to let you add him, then you can chat with him.

On the other hand, you can chat in 'Room'. This can be done by clicking MESSENGER/YAHOO! CHAT/JOIN A ROOM. You just need to select a desired room.

try upgrade messanger

the issue as to do with connection of the chat room, try another chat room like tagged and all other network that has chat room to know if it is the connection

When you have the Yahoo! Messenger 9 window open (with your friends and whatnot) go to Messenger, and then Yahoo! Chat. A sidebar will come up next to Yahoo! Chat with the options Join a room, create a room, and favorite rooms. From there you can choose which you want to do.

I installed the most recent version of Yahoo! Messenger 9 just now and that's how it's set up for me. :)

Hope that helped. Have a great evening and please don't forget to rate this solution.