After a few hours my network doesn't work on my laptop. There appear a lot of those messages:
eth0: NULL pointer encountered in Rx ring, skipping
eth0: NULL pointer encountered in Rx ring, skipping
eth0: NULL pointer encountered in Rx ring, skipping
eth0: NULL pointer encountered in Rx ring, skipping
eth0: NULL pointer encountered in Rx ring, skipping
eth0: NULL pointer encountered in Rx ring, skipping
eth0: NULL pointer encountered in Rx ring, skipping
eth0: NULL pointer encountered in Rx ring, skipping
eth0: NULL pointer encountered in Rx ring, skipping
eth0: NULL pointer encountered in Rx ring, skipping
It works again after restarting network. I'm using 2.6.8-rc2 now. It was the same problem in 2.6.7, but I didn't test it with earlier kernels.