What does the first size refer to, if not size on disk? Where else does the file exist other than "on disk"? I guess the "on disk" figure could be rounded up to the next 4k boundary or something (it's a multiple of 4096).

I've no idea why the import isn't working for you. I've not heard of anyone else having that problem. I hope the bootstrap.dat file isn't corrupted. Did anyone else try using it recently? If so, how did it go?