I run my NAS on an Intel SS4200-E  using Debian Stable. Since the SS4200 doesn’t have a graphics device, I use a serial console. Good set-up instructions can be found in the SS4200-E Wiki . After the upgrade the kernel was not configured accordingly and I lost contact via the serial console. To complicate things, Squeeze upgrades the grub package to grub-pc (AKA Grub Version 2).
Here are some notes on how to fix this. The first step is to get the system to boot with a serial console by editing the kernel parameters. Use Grub to temporarily add these parameters to the: console=tty0 console=ttyS0,115200.
Once booted, make this permanent by adding the following to /boot/grub/grub.cfg.
GRUB_CMDLINE_LINUX="all_generic_ide console=tty0 console=ttyS0,115200"
GRUB_SERIAL_COMMAND="serial --unit=0 --speed=115200"
Run update-grub2 to apply the change. This will update the new Grub2 configuration in /boot/grub/grub.cfg. You may want to edit the old /boot/grub/menu.lst to add the same changes if you are still booting from the old menu.
 – http://www.intel.com/products/server/storage/ss4200/index.htm
 – http://ss4200.pbworks.com/w/page/5122751/FrontPage