To fix this you'll need to do a few things.  Depending on the type of database you have, will determine how you handle these steps.

1. Make a backup of your database.  You'll be editing a row on your database.

2.  You'll need to access the "user" table in your helpdesk database and look for the "admin" Login. 

     Should be in one of the first two row.

We've included two screen shots to reflect the changes you'll need to make for that row. Make the changes then restart tomcat.