login user account not showing up on restart

I run a small business. My assistant left and a new assistant has been hired. I changed the name of the user account for the assistant to the new assistant. Logging between the User (admin) account and the user (assistant) account works fine. When you log out all the user accounts show up.

However, when the new assistant went to startup the iMac in the morning only the User (admin) account shows up. Her user account did not show up.

I tried restarting the computer with command-r and going to the terminal to reset the password and this procedure is a no go because nothing shows up in the accounts dialog to reset.

So, what do I need to do to make this iMac functional? I don't want to give administrator rights to the assistant and that's why I have a user account for her, that is different than the administrator user account. Do I need to wipe the harddrive and start again.

I do have filevault on. The computer is running the last update to lion.

I appreciate your suggestions.