We are supporting Cloud9 products mainly for reactivations issues and general installation questions, but making improvements to the scenery it's more difficult for us.
This issue has been like this since the scenery was released in early 2007, strange some complains are surfacing only now, apparently people were less sensitive to small visual artifacts back then. It's also probably released to the fact ENBR was made before FSX SP2 came out, not sure if this makes a difference or not, but it might.
I'm not sure right now if we can fix it or not, we have to look into it but, as I've said, it's not as easy for us as fixing an FSDT products AND I had an email recently from an user that said he was working on the scenery and improve the flatten. He'll send me the file and will also upload it here when he's done, perhaps this will fix the flickering as well.