Flickerling fences and runway lights issue

Hello

Hope someone out there can put me out of my misery with a problem I have with FSX. I have two issues that may be related, both seem worse with add on scenery rather than the default airports.

The first problem I have is that I suffer with really bad flickering but only on fences and lamp posts especially with both of the  2 add ons airports I have purchased, (UK2000 Gatwick and Luton). I have tried various configurations of AA and AF both via the CCC and in FSX itself but with no luck, I cannot enable AA in FSX directly as I suffer continuous flashing black screens, tried a reinstall with no luck. The fence problem is not so noticeable at night, My CFG config file has been modified the bojote tweaking tool but I have tried an unmodified one with the same results.

The second problem I have is that I suffer with flickering runway lights when they get to be a certain distance away from the runway I did think that maybe it was due to my aged PC and ATI 4870 card but the stock airports are fine and i get a good 25-35 FPS.

any ideas?

Many thanks

Darran