Sapphire Radeon HD3850 color banding problem

Looking for some help with my new card.

Recently upgraded from Radeon 9800 128 Pro to Sapphire Radeon HD3850 512mb AGP. I have about 20 flight sims which all run fine previously. Now there is banding in the sky for about 5 sims, JAS, F-15, FA-18, EAW, FS . I have researched this for hours with no joy. When the banding occurs it looks like the colors have been set to something very low (8 bit?).

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WINXP computer

System specs

MOBO ASUS A7N8X Deluxe v2.0
OS Windows XP SP2
RAM 2GB matched dual channel
PROC Athlon XP 3200 , 2.2 GHz
Graphics Sapphire Radeon HD3850 512mb AGP
Sound Built in
HDD 80MB, 120MB
Drives Plextor DVD RW, LG DVD super-multi, Floppy
NIC Built in
Power 550 watt very high quality supply

Joystick Logitech Extreme 3d Pro


EVALUATION - Sapphire Radeon HD3850 512mb card

Good for FSX, Flaming Cliffs, Blackshark, which would not run before.
Did the driver-dance for about 5 different versions, 8.1 (CD came with card) really horrible, 8.4, 9.10, 11.11, 12.6 looking for the best one. Since I have about 21 sims and each must be tested with the driver, you may imagine what a chore this is. Settled on CAT v9.10 because it had the least problems.

CAT all tested versions.
PROBLEM: Banding of the sky occurs in F-15, FA-18, FS-DOE, EAW, JAS, crash on exit from USAF Super Pro 9
FIX: Never solved in any driver version.

I would really like some helpful advise on this issue. It really bothers me that this high end card does not perform as well as a 4mb AGP junk card for the above mentioned sims and the color banding problems. Am I forced to accept this degraded graphics performance?

Have a great day,
tplummer