Do you mean MySQL stopped working or that phpMyAdmin will not let you into your databases any more.
The order of event is supposed to be:
1. add a password to the root userid ( using phpMyAdmin )
2. Change the phpMyAdmin config file ( like you did ) to use the password you set up.
So change the phpMyAdmin config file back to have no password and allow NoPassword, then start again at point 1.
Read this.
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forum.wampserver.com]