I'm sorry, but if you see *most* of the buildings, just missing one terminal, it's nothing related in any way to installation or antivirus. You wouldn't see anything, if this was the case.
Most likely, it's a problem with your video drivers or settings, or video memory corruption.
Try all the following:
- Update your video driver
- Reset your video driver settings to default
- Reset the FSX settings to default, by removing the following file:
%APPDATA%\Microsof\FSX\FSX.CFG
This will force FSX to rebuild a new config with all default settings. After doing this, be sure you apply the HIGHMEMFIX tweak in the Addon Manager, save the settings and restart FSX.