I would check the scenery priority order or something to do with the shader's cache.
To fix the "square phenomena" probably related to your ORBX stuff, and to enjoy
all the visual effects only possible on DX10, take a look at Steve's DXfixer. Not very
expensive and, for GA pilots, the addition of shadows in cockpit, worth it.
i7-4790K @4400 on Gigabyte Z97X (16gb), GeForce GTX 970 OC, Corsair Spec case
Win7 Ult(64) on Samsung850 SSD(256), FSX+Accell on Samsung850 SSD(128), Track IR5
Saitek yoke/rudder radio/multi/switch panels, Logitech G13, GMap on Samsung tab