Some Windows 2008 R2 servers may experience Reboot problem. If these servers are using File Share or SMB v.2, srv2.sys may cause this problem.
Srv2.sys driver is root cause of this problem. This is SMB 2.0 server driver. You can download hotfix KB2552033 for Windows Server 2008 R2 SP1 with your own risk until Microsoft officially release it.