I'm a newbie in netbsd, but not in unix and networks.

I'm trying to run netbsd 1.5.2 on a KA-650 cpu, and when I configure
ethernet card (I try with deqna and delqa to), I got many message:

qe0: discarding oversize frame (len=1980)

but the ethernet cable _isn't_ connected. Mtu is default (1500).
What's this?
If I connect to the network, I got more messages, and the system is
hang up after few seconds.