I'm trying to use the client.eye var to let the user enter a sort of sniper mode. However, sometimes when moved so far the screen turns completely black. What's the reasoning for this so that I may fix it?
Check out client.perspective. Basically what's happening is your clients mob can't see the objects so they're not showing up (because client.perspective defaults to MOB_PERSPECTIVE).
In response to DarkView
i've had this before and found that this works...

//src or usr or M however it is in your code
src.client.eye = locate(x,y,z)
src.client.perspective = EYE_PERSPECTIVE