I am having the same issue when running CyanogenMod 7 out of a uSD card. The app runs, I choose a book and then it crashes. This is since the update that includes magazine reading functions.
Not much to say. I am learning to use the Android development tools, and I have a Nook Color running CM7 out of a uSD card. I am waiting to see how the new update goes before installing CM7 to internal memory.