You might want to upgrade two things: kernel to 2.6.10 and your VDR. The kernel because it fixes things in the video4linux driver (at least for me), and VDR because it had problems with threading and some ring buffer overflow in 1.3.18 IIRC.

Still happens in VDR 1.3.20. The kernel is 2.6.9 but the DVB driver is a recent CVS snapshot.

Olaf