Yep it is normal. There was some answers about this and I think how to go about removing it on the oztivo email digest some time ago. Pop on over to www.oztivo.com and do a quick search as it should turn up what you are looking for.
Edit: I just went and typed in green line in the search window and it pulls up a heap of stuff about it in the email monthly digests. Note there are two "green line" issues: One is the issue you are referring to and the other is a brief horizontal green line flash withich is a fault in the video chip and nothing to do with your question.
Good luck.
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