So... Another case of "Unable to MapViewOfFile in MapChunk," but something odd this time.

If you are still having frequent crashes, you can turn your Texture Quality down even further by manually editing the production_Config.ini file. You can find this file in your Documents/My Games/Path of Exile folder. If you find the line texture_quality=1 and change the number to 3 or higher, you'll reduce the texture quality even further. Note that this may make it much harder to see some enemy spell effects, however it may help you here.