Close
Half the problem seems to be that Greyc-helper.bin is not set as LargeAddressAware, so it crashes at 2GB instead of 4GB. After fixing that, it can now process much larger images without crashing.

Here is a x64 build with LargeAddressAware enabled on 32-bit Greyc-helper.bin: http://www.mediafire.com/?aypsi20c5vvv53s

Though even with LargeAddressAware, Photoshop throws an error about not enough memory and refuses to launch the plugin for document sizes >2GB. So it would seem that's the real maximum limit, with Greyc-helper using slightly less than 3GB of RAM during processing on 1.99GB docs. Not a major issue since 2GB docs are quite massive, but it would be nice to see that limit loosened to 3GB docs on x64 builds to give a bit more wiggle room.