Yo larry, skunk is right about the objects limit of 255, if you zoom out (keep going higher), then zoom in, the stream should be ok for the area you are viewing.
That's the problem with big maps (hundreds of objects), the MTA Race Editor just can't handle it.
Maybe try the new MTA DM Editor? Harder and slightly slower, but can handle loads more objects and to be honest, the menus are a lot better too.