I wanted to try out the Cyanogen 6 Mod that I've been hearing so much about, so I did a nandroid backup of my Stock (Leaked) Froyo, and then installed the Cyanogen Mod. When I decided to switch back to stock though, I ran into all kinds of issues. My bookmarks disappeared. My settings were all switched back to default. The update I had installed to fix the problem of apps not appearing in the Market doesn't work anymore.