Road America graphics glitch (with Video Proof)

Ok I was racing with the AI on Road America and on the penultimate lap some of the trackside graphics went weird, with some trackside objects turning pink and others having a strange patchwork effect to them.

Ive included a video to show the bug in action so to speak, the first lap you will see is ok nothing wrong with the graphics then at the end of the first straight look at the trackside and you will see pink blobs then as the race continues more graphics anomalies show up.
Just to preempt the standard answer to turn off the Xbox and reboot I never keep my Xbox on standby and always unplug after I have finished gaming so my xbox is always booted afresh. This problem doesnt happen all the time as you can see by the first lap being ok, and its only started after the Long Beach update. has anyone else experienced this strange bug.

VIDEO

List 'o possibilities:

  1. Texture not loading. It appears to be just one or two actual textures missing. That could be corrupt install data, or could be not reading from hdd (like a bad sector possibly)
  2. It could be heat causing the GPU to not display stuff correctly, but since it does not affect the entire screen I would think this scenario is highly unlikely.

First thing I would try would be to delete the disc install data and reinstall it.

Thanks for the reply Turns, what is confusing me about this problem is why doesnt the problem start at the start of the race i thought everything thats needed for the race is loaded into memory so if it was a problem with the HDD then i would see the corrupted textures from the start. As for the GPU overheating as you say its highly unlikely as i would see problems in all games not just this one track on Forza.

Could this be a bug in Forzas memory management i dont know but anyways to everyone reading this keep an eye on this track to see if you get the same problem as i said in my OP i only got this problem after the Long Beach update.

Im having the same problems only it is on the nerbering and the indy oval. In the indy sections of the road go black and I have a vid of that and the nebering I see the backrond rendering is choppy and not smooth as if the fram rate was slow and not the road.