Spray them with some fungicide and cross your figers. If the corms are still hard then they should be fine.

Wow, that was fast! Thanks, I'll give it a try. The corms are mostly mushy (I think). :(

Fungus/mold tends to form along the dead portions of M basjoo plants, but does not harm the living corm or whatever part of the stem is still green - once growth begins, the leaves quickly overcome the mold.

Thanks xerophyte, you've given me some hope!