I don't know why, but every now and then when I try to memorize spells, I find that not only can I not do it, poking around in GBC shows that all of my spells have been completely erased. The only things I can think of to do are reload when it happens, or try and use GBC to give myself my spells back. Has anyone else had this issue, and if so, how do I keep it from happening?

I had this too. The only thing that worked for was to use GBC to reset spells. I'm not sure if the problem comes from GBC itself but at least it provides temporary solutions. A really annoying bug.