This issue has occurred on both Windows 7 and Windows 8 machines. My computer is a member of an active directory domain Foo and I map a network drive using credentials to a remote domain Bar.
Anytime I reboot my mapped network connection to the Bar domain is lost.
When mapping the network drive I use Reconnect at sign-in and connect using different credentials. I enter the credentials and check mark save credentials.
Yet every time I reboot I have to go through this process again.