I've had this on a couple of missions where I have continued on from alternate points.
The game starts creating large white squares and wipes out tiles. There are also strange white triangles.
They occurred into both of the following attached....although are not present at the start of the snow death save.
The other save is borked from the start.
http://www6.zippyshare.com/v/8825797/file.html
http://www6.zippyshare.com/v/28876506/file.html
Neil
base death.sav
Snow death.sav
base death.sav
Snow death.sav