MSFS2002 addons Problems...maybe?

Hi again girls,well my nightmare is upon me again. Maybe a literate videos person can enlighten me. Problem: After I downloaded and installed "FSWGroup Clouds Pack 1", and also "MSrees.zip" my video seems to have lost its clarity (maybe its a smoke effect within the FSW program)! But worse I notice the "new" trees seems to be "bubbling" and "jiggling" as I fly over. They seem very "busy" and glitter like they are vibrating back and forth.I know I can remove the trees (I made backups of the defaults thankyou)and start again fresh but I'm wondering if I have missed something in my video set up in windows. I have a Radeon 8500 ATI with 64 Ram, my system is a 2 ghz Athlon with 512 DDR. All boxes are checked off in the "Hardware" tab but still the "bubbling" trees exist. I'm not sure what to under the windows "Control"/ Display/advanced/ video graphics set up but I'm trying everything short of uninstalling the addons.Finally can anyone explain to me which "refresh" rate I should select in the Graphics set up? My video will refresh itself from 75mhz to 125mhz and I never know which to peg it. Is a higher "refresh" rate better for MSFS than a lower one? It is at 85MGzThanks for help from anyone.JoeKMCO near Disney World