I have Canna bulbs and Dahlia bulbs which I dug out of the garden in the fall. I let them dry out a bit and havestored them in the basement. I just checked on the bulbs and some of them are dry and rotted.

So you have some bulbs in storage which are drying out. Make sure they are in the coolest location in the basement or you can put them in the crisper drawer of your refridgerator. If the bulbs have already dried out there's not much you can do to re-hydrate them. To avoid this problem in the future, nest the bulbs in peat moss of vermiculite and store in a cool location.