Do you know why the connection switches between connect and disconnect without ever making a connection to the scanner?
There could be a couple of causes for this issue:
The cable you're using is faulty therefore triggering the connect/disconnect issues.
The port where the cable is attached is malfunctioning. Try switching to some other port.
The drivers are not installed properly. Use the CD or the installation package to reinstall the drivers.
The device might be faulty, which again triggers the connect/disconnect event.