Kinda Learning, but still have a problem

[BE58D]

Someone created some scenery that shows Meigs Field being closed, I didn't care for the way it looks... so, I decided to try it myself and I got the X's (closed markings) in place. But, this is my problem (look below).

My textures flash and do weird things, what can I do to stop this? I am using just a flat poly and even tried to make the part itself a solid color (no texture), the only problem is... that way only half of the X is yellow, so it looks more like this... \

Someone, anyone?!

[BE58D]

Problem fixed... Thanks for everyones help! :-/

I simply took a tube and flattened it, instead of using a flat poly.  Works fine now.