The network connection is causing short

It's normal for a switch to flash some when a new device is plugged in. Of course, things should normally settle down within a few seconds.

First question. Are you hooking up both ethernet connections? If so, don't do this as that will cause problems unless you are using managed switches and configure the links properly on both ends. The behavior you describe would be consistent with creating a loop in the network like this.

Assuming the above is not the case and you still have a problem, you'll need to snoop into the network a bit to find the cause of what's going on. Since the network is being locked out by this it's almost certainly some bad broadcast traffic which is hitting all ports. The good news is that if that is the case it's pretty easy to capture.

Go to www.wireshark.org and download wireshark. It's free and pretty easy to use. Load it on any computer attached to the switch and experiment around a bit with starting captures and sorting through the packets to get an idea of what normal traffic on your network looks like.

After this, plug the offending computer in and see what happens. The problem packets will probably be very obvious although what they mean or how to fix things might not be so obvious. If this is the case, just post what you find and we'll take it from there.

Good luck and let me know if you run into any problems.