packet loss after Lenny Squeeze upgrade

[Bonno Bloksma <b.bloksma@tio.nl>]

Hi,

I have a Debian server (hardware HP DL360) which I use for internal routing and which uses NAT to isolate a part of my network.
This machine has been routing for the past few years without any problems but lately there is a lot of packet loss for the traffic going to/through that server.

What has changed in Debian that could cause this and what can I tweak to get things going again?
What do I need to look at?

The server hardware does not seem to be the limiting factor, cpu is a max 10%, memory seems to be ok.

Bonno Bloksma