You have had, in the past, no trouble connecting to VPNinja with my account, but you are now getting an authentication error with all the servers.
Case #1: Your VPNinja account has expired.
Albeit rare, even a ninja in the heat of battle can forget whether or not he left the stove on. Everyone overlooks details sometimes; stress at work, a new awesome set of nunchukas, or the daily grind of damming the man. The point is it happens to us all, but the solution is very simple:
Just head to http://vpnninja.net, login with your account credentials, and choose the package that best suits your needs.