There is a console port on the back of the switch. Connect to the console port and you will have access to the CLI. Once connected to the CLI it should lend some insight to what is happening.
The ports lights on our PowerConnect 5448 are blinking very quickly in unison.  We use this switch for a desktop network.  No servers or computers are available on the network.  We believe this was due to a power outage that caused a failure with our internet connection.  We restored power to the modem and re-booted the firewall since it was off.  Then we noticed the lights on the switch.  We manually powered off the PC 5448 switch and then powered it back on.  The switch still shows the same problem.  We can directly connect to the modem so we know we have internet.  It appears something is wrong with the switch due to the blinking port lights. In addition, the admin user and password to log into the switch are lost, so we cannot see what is going on.
PowerConnect 5448 Port lights blink up to 10 times per second in unison