Thread locked, as the cause to this was found and information about it was posted in the
Common Technical Problems thread:
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EOUTOFMEMORY or Unable to Map File or Unable to MapViewOfFile
This usually occurs when your game file runs out of ram, common on PCs with low ram or running 32bit versions of windows. Running the game with Texture Quality set to Medium usually fixes this, though having less than 4gb of ram will cause problems after changing areas a number of times. We will improve the memory recovery system in future.
You can also reduce the rate of these crashes slightly by adding -gc 2 to the end of your Path of Exile shortcut target, as shown here:
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 2, you'll reduce the texture quality even further. Note that this may make it much harder to see some enemy spell effects.