because of the memory consumption i would say, it's a lack of available memory - as the message says.
So try out to save in a lower resolution. You'll find the "Option" button, when saving as STL.
And the other thing, i would recommend, is to rise the swap file size in Windows.
Thanks for the suggestion, Heiko.
I just changed the swap file to a maximum size of 24GB, but it still gave the same error.
I have the resolution set to 'Coarse'
I'll keep trying.
that's not a maximum size a swap file can be. it's only 1.5x ram. you could go even 3x that. depending on your available size on HDD