I just installed Ubuntu 9.04 on a brand new Acer Extensa 5635Z laptop, but ethernet networking does't work (wireless doesn't work either, but I'd be happy with ethernet for now).

eth0 isn't listed in /etc/network/interfaces:

$ cat /etc/network/interfaces 
auto lo
iface lo inet loopback

lshw does show the nic, but I can't make much sense out of the information:

$ sudo lshw -class network -sanitize
  *-network DISABLED
       description: Wireless interface
       product: AR928X Wireless Network Adapter (PCI-Express)
       vendor: Atheros Communications Inc.
       physical id: 0
       bus info: pci@0000:07:00.0
       logical name: wmaster0
       version: 01
       serial: [REMOVED]
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress msix bus_master cap_list logical ethernet physical wireless
       configuration: broadcast=yes driver=ath9k latency=0 module=ath9k multicast=yes wireless=IEEE 802.11bgn
  *-network UNCLAIMED
       description: Ethernet controller
       product: Attansic Technology Corp.
       vendor: Attansic Technology Corp.
       physical id: 0
       bus info: pci@0000:09:00.0
       version: c0
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress vpd cap_list
       configuration: latency=0
  *-network DISABLED
       description: Ethernet interface
       physical id: 1
       logical name: pan0
       serial: [REMOVED]
       capabilities: ethernet physical
       configuration: broadcast=yes driver=bridge driverversion=2.3 firmware=N/A link=yes multicast=yes

Thanks for your help!