MySQL 5.5 accepts password but then closes connection
A) Try with 


mysql -h[your IP] -u[username] -P[]port -p
mysql -h127.0.0.1 -u[username] -p
mysql -hlocalhost -u[username] -p


Which one works and which does not? 

B) Set Log_warnings=2 in my.ini and restart MySQL server and see error log entry when connection gets closed abruptly.