Which system did you use before? If your previous system is Windows XP Professional, I suggest you clear the cache of your profile that was saved form any Windows XP clients from the server side. Otherwise, you need to be allowed to create a new profile storage folder whose name is [username].V2 on the server side. You can also manually create such folder.
Managing Roaming User Data Deployment Guide
Network connectivity problem can also be the root cause. Incompatible drivers may be disabled when you try to end the session of your logon. Please find Windows 7 compatible driver and install. If the issue persists, please temporary disable antivirus and firewall on the client computer.
If the above suggestions do not help, I suggest you open Event Viewer, view the logs Windows Logs/System and Windows Logs/Application. Try to find some clues.
Hope it helps.
Arthur Xie - MSFT