wave64 is sony wav file, greater than 2 gigabytes Memory usage is about x64/x86, but library developers are already using a x64 version of nat.
What's interesting, the disk limitation is more important than memory limitation, because deconvolution works as a stream. So now you could create a testtone composed by many steps and it could be greater than 2 gigabytes and deconvolution could be executed on a common nat 32 bits.
are you creating new files? do they work when they are smaller? When they are big can you generate them? are they correct? How much big? did you try something from 2 gigabytes to 4 gigabytes before going further? keep in mind each single dynamic sample inside each big testtone file can't exceed 2 gigabytes, but I don't think it is the case.
try to use the betatesting forum (this is the wrong forum) and send your session (xml/n2x files, saving them somewhere), so I can understand what are you are doing (telling me: "it doesn't work" really doesn't help, the subject is missing!).
about nat3cmd, don't use it. Really you just need to install nebula 64 bits, BUT nat3cmd is a command line utility. Common nat3 supports big files now, I tested a 2.8 gigabytes file which is greater than a common standard wav file. Btw: you can't copy ippcore-8 from a 32 bits application, you need ippcore-8 from a 64 bits application. Which is nebula 64 bits. Anyway forget nat3cmd, it is for multi-sampled eq only.