A recent upgrade of my server to Ubuntu 8.04 beta forced me to solve an issue I have been having with the integrated MCP55 ethernet and recent Linux kernels. At boot the network interface appears to come up and shows as up in ifconfg. However, it just will not work. Eventually I found a fix on the Gentoo Wiki. However, adding the forcedeth module options specified to /etc/modprobe.d/options did not fix the problem. I think that the kernel is loading the module from initramfs and that needs to be updated as well. This  is what fixed things for me.

Add the following line to /etc/modprobe.d/options
options forcedeth msi=0 msix=0
Then rebuild initramfs like this
sudo update-initramfs -u

BTW – this was the only issue I came across doing the upgrade over ssh. Everything else worked perfectly.