I updated 3.1 on a Dell Inspiron 3500 and now find on 4.0-beta I'm 
getting hangs due to 'rtk0: watchdog timeout'. Is this a known 
problem?

I must have copied over several GB on 3.1 without problem whilst 
trying to install Ubuntu an Win98 to multiboot on same machine.

'ping -c 1 servername' gets the link going again but means it can't 
be left unattended.

From 4.0-beta2 system (GENERIC_LAPTOP):
rtk0 at cardbus0 function0: Realtek 8139 10/100BaseTX
rtk0: Ethernet address ......
rlphy0 at rtk0 phy 7: Realtek internal PHY
rlphy: 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto

Ubuntu sees it as RTL-8139C so is it worth build of a kernel without 
rtk and just having re driver available?

David