David,
"Server & Gateway" with just one nic installed seems a bit "unnormal" to start with .-)
Else:
Start "top" and have a look at what processes are running when you see these "led flashes".
Look at the dmesg log file to check wether there is some substantial problem with your hardware. Look at the messages log to check for more.
"Some" flashing needs to be going on in a multiuser/multtask OS which is NEVER idle

Good luck