I had the exact same problem. I messed around for hours before I found a weird solution. I deleted the corrupted save file via the wii data menu, used a dvd, ran it from a loader (neogamma) and it went straight through the save phase. The hdd backup then worked fine with hermes 222 or waninkoko 249 using cfg loader v70.
Examining the save files it would seem that data.bin was being created but save.dat was not. Why this phenomenon occurs I'm afraid is beyond my knowledge.
HTH!