Mega really doesn't like 32 bit browsers so I'd check that for it failing downloads over 2 gigs. I've also previously had issues with winrar and this game in the past. Just install 7zip. It's free and in most cases just better in my opinion.
Had this issue before with winrar. Try updating your prefered unpacking software. Or install 7zip.
Getting an unexpected end of archive or unknown file format errors when extracting both the windows 32 and 64 bit versions
