Hi wallabybob,
That's great advise.
After enabling polling and rebooting, my problem has seemed to go away.
I'm not entirly sure if polling did anything to help it - it may have just been the reboot! But if the problem comes back I'll be sure to refer here to quantify the interrupts generated.
Just FYI, I was trying to do a samba (CIFS) transfer at the time over an openvpn connection (The openvpn server being seperate from the pfsense box) to a remote openvpn client in another country connected via a DSL connection (8Mbps down and 832kbps up as pfsense sees it).
Before the reboot, pfsense GUI and shell access would be non-exsistant after about 2Mbps or transfers down from the remote server. After the reboot, I can hit 6Mbps (which is the max that this openvpn connection can reach for some unknown reason) without any problems.
The speed measurements are from pfsense's traffic graph. Before the reboot, I knew that pfsense would become unresponsive at around 2Mbps as that's when the graph would stop working..
Cheers
JT