So I've been having an issue in FSX:SE recently similar to a problem that was in FS9. Upon reaching high altitudes (around the point where contrails form), rough water textures would load on the horizon, thus resulting in ugly jagged boxes and obviously unfinished textures. I haven't had this issue in FSX until recently.
Here's an example:
As you can see, there's brown-colored water off in the distance. Here's how it looks when you Slew over it:
I'm not quite sure what's causing it, or how to fix it (except for reinstalling the sim). Any tips?
Lower some of your slides (autogen, shadows, clouds, AI).
It may be to graphic intensive for your video card or computer.
Let us know if this helps.