OK stop.
*Unplug all microphones and XLR cables. Don't plug them in again until the problem is sorted.*
If the interface is acting up without microphones plugged in, turn off phantom power and see if it still does it.
If so, get on google and make sure your drivers are up to date and compatible with your operating system AND change the usb/firewire cable and port.
If you're using a hub, don't. If you're plugged into a front port, go for a rear one instead.
If you're plugged into a rear port, plug into a different one.
If you update drivers, restart the computer.
If you do ALL of these things and the problem is still there, take the interface to a new computer.
If the problem exists after all these changes and on a new computer, you may have a faulty interface.