I’m currently using Windows 8 Enterprise edition at work and one of the first problems I ran into was that none of my drives would stay mapped. Even when I selected “Reconnect at sign-in” most of my drives would disappear after a variable amount of time. I could always remap the drives, but they wouldn’t stay mapped which was incredibly frustrating.
I’ve learned that this can happen if you are running with administrator privileges on your machine and that machine is connected to a domain. I’m not sure of the details on why but I do have the fix that worked for: