Just wanted to put this out there.
If you are using the old NAT +Proxy reflection I have seen this causing the systems to crash once I started pushing more data. My spec is
Via 1GHz 512MB RAM using ET0(PPPOE) and ET1.
After switching to PURE NAT this seams to of resolved my problem.
Pure NAT mode scales much better than proxy mode by the nature of how they function. If you have a lot of reflected connections, don't use the old NAT+Proxy.