If the Integration Server detects a problem with the master password or outbound passwords at startup, it will automatically place you in safe mode. You will see the following message in the upper left corner of the Server > Statistics page of the Integration Server Administrator:

These problems can be caused by a corrupted master password file, a corrupted outbound password file, or by simply mis-typing the master password when you are prompted for it. If you suspect you have mis-typed the password, shut down the server and restart it, this time entering the correct password. If this does not correct the problem, refer to When Problems Exist with the Master Password or Outbound Passwords at Startup for instructions.