That's a firmware problem. The band is well-known and can be forced on most cameras when shooting in low light. The band appears about .58 of the way across the frame. Sean Reid said he spoke to the Leica people in Solms and that it will be fixed in 1.10
For more see the thread here, on the Leica forum:
http://www.leica-camera-user.com/digital-f...highlight=bandsBe aware that there are a number of banding problems, some of which have been fixed. But the one you show also has a darker "scratchy line" effect in addition to the .58 band, and that scratchy line effect (also known as rainbow lines) can be sometimes generated if your camera goes to sleep, and you force it to fire without first waking it up. You can avoid *that* effect by tapping the trigger once, waking the camera up, before you take the next shot.
JC