I have a sonicwall TZ170 firewall with intrusion prevention, email attachment filtering and gateway antivirus. It's been working just fine in my network for about 8 months.

recently, the LAN indicator of the firewall started blinking very fast in an unusual manner. after a little while, all light indicators on the network of all the devices (switches, hubs, NIC's) did the same blinking behavior in the same fashion. I have noticed that when the firewall is disconnected, the behavior of the network is usual and peaceful. But, bringing back the firewall into the network would cause everything to blink so wierd and some times it even causes the network printers not to print and some client-server applications to fail some tasks.

I use Norton Antivirus Corporate edition which detects all the viruses usually and cleans them up. I used it in addition to AVG and stinger and made sure all the computers are virus-clean. However, the weird behavior of the network/firewall still persists. Sonicwall sent me a replacement unit of the firewall which worked fine for one hour only, and then started that weird light indicator behavior. I'm about to have a heart attack here because of this mystery. It's so confusing and unpleasant. I don't know exactly what's causing this problem. Especially that I disconnected all the computers from the network but the firewall light doesn't want to stop blinking like crazy anymore.

Does anyone have any useful comment/suggestion/knowledge of this issue? Help is highly appreciated.