Loosing aeroports buildings when landing at night ?

Hello all,Yesterday i flew the Feelthere ERJ from CYUL to KFLL (FSDreamteam); started at dusk so arrived at night. i used ASA and Radar Contact on my client PC.All along the flight, spot view shown clear and crisp ground detail in between clouds, right up to 3000' when i was vectored west from the coast to land on 9R; the problem is, on final, i could see the runway lights but no airport buildings ?! after landing and ending FSPassengers on the taxiway, i restarted FSX and position myself at the gate at KFLL and sure enough, buildings were there with FPS at 12-15 locked at 20.Also, might be relevant to mention that, on others flights when i ended the FSPassengers flight and came back to the plane to start another journey, more often than not the screen would turn black or all the graphics would be distorted ?! this happens mainly at night, also sometimes when i access map in flight and try to come back inside the plane....I also use GEX, UTX Can and USA (With lights at intersection only), road traffic at 9%, MyTrafficX at 59%, autogen at dense, water at 2X mid, at 1680 X 1050 resolution, with Nhancer set per NickN instructions, fsx on it's own 640GB drive, defrag with O&O.My PC is an HP Elite e9180f which i replaced the Motherboard with an Asus Rampage II Gene with an I7 920 overclocked to 3.2 ghz (with Asus's Turbo V feature), 9gb of DDR3 10700 memory at 667mhz (according to CPUiZ) and an nVidia 250GTS with 1gb dedicated memory with 182.50 drivers. when in flight, cpu temps are around 65 degrees Celsius.Sorry for the long post but my question is this :Is it a memory issue (bad quality or bad timing ? ) or the 250GTS graphic card not powerful enough? (might try my 8800GTX just for fun...)thanks in advance for the tips :( Alain from Montreal