I have been fighting a problem for years that I may finally have a clue about. If you access a network resource, turn on offline flies for any file or folder, and do not save your authentication to that remote system -- Offline Files will never allow that system to prompt you for authentication ever again. I have a Windows 7 Pro installation on a laptop that switches networks very often and I've tried to use Offline files to manage file access while I'm off of a particular network. The laptop is not joined to a domain and access remote files through UNC shares like \\computer\share. Typically what I experience is that after connecting to the network, Sync Center Offline Files refuses to acknowledge the remote system is available. All synced files that you've made offline can be accessed, but non-synced files are inaccessible. I can ping the system successfully, and I can access the share from another computer confirming it is absolutely operating and available. Sync Center > Offline files shows the system as "Disconnected:" "Work Online" disappears and no longer becomes an option when browsing the offline folders in question. There is absolutely no way to convince sync center it can reconnect even though it can. I think I discovered the underlying problem after throwing my hands up and turning off online files permanently. As soon as I disabled offline files, rebooted, and tried to access the same network resource -- I got a username / password prompt. What I believe is happening is that offline files is blocking the authentication request from bubbling up to the UI. It is connecting to the network resource, getting denied access, and deciding that resource is not available. Since you can never be prompted for auth, the non-synced files become unavailable indefinitely. I've tested this theory by storing authentication in Control Panel > Credential Manager. So far I've been able to disconnect and reconnect to the network multiple times and offline files has been able to reconnect and detect the remote system is available. Time will tell to see if this is a solid work-around. My suggestion to any MSFT folks reading this post - please put in a bug report somewhere that offline files blocks authentication prompts and can create a situation where remote resources can never be accessed again?