Martin Held wrote:

> I have running NetBSD 1.5.2 on a Sony VAIO PCG FX 505 Notebook and
> a problem with the internal Ethernet (RealTek 8139 10/100BaseTX).
> 
> When i try to ping some other machines in the network i got only "rtk0: 
> watchdog timeout"

Use a newer kernel e.g. a Snapshot of 1.5Z[ABC] or compile a current one.
I had the same problem with 1.5.2 on my new PC.