The forcedeth driver for nVidia NICs had some interrupt handling issues in earlier kernels. However, as Debian/etch is still using 2.6.18, these boxen may still get flooded with messages like:

eth0: too many iterations (6) in nv_nic_irq.

A fix has been posted in 10/2007 (~2.6.22?) and as a workaround we could put the following into /etc/modprobe.conf:

options forcedeth max_interrupt_work=10