Hmm, this happens occasionally with my L1020 - but my L1020 doesn't have Rich Capture. My observations indicate that this happens when the phone "is doing something" at the moment the photo is being saved, e.g. some of the live tiles are being updated or an app is at a certain stage of installation in the background - all of which seem to indicate that it is background/total RAM usage that causes those lines.
The occurrence is very rare and difficult to catch, but having Rich Capture enabled could also aggravate memory/RAM usage.