Read the Changelog its in there for people who can read.
> Jul 11 05:16:52 aitsu kernel: Call Trace: [<0013afb5>] [<001395e9>] [<0013a04a>] [<0013a58f>] [<00150af3>] [<001368d9>] [<0012beff>]
> Jul 11 05:16:52 aitsu kernel: [<0010a5f5>]
> (these three 'eth0' errors display about 15 times more, then stop as if
> nothing ever happened -- eth0 at this point doesn't work, but the machine
> is booted and acts fine).
Go through the System.map for the kenrel and look up the call trace. It
looks like on your species of card the tulip driver dumped core and broke.
All we need to know now is a) where b) why
Alan