NW6.5SP6, BM3.9, SC6.1

Surfcontrol dies after a few weeks ... works fine after rebooting the
server, then after a while I note that it stops working. It's still
loaded and appears to be running. I can change rules, save, but it still
doesn't work.

Unloaded CPFILTER and reloaded, still no joy.

Any suggestions anyone?