KB Article: http://support.microsoft.com/kb/2001877

INTRODUCTION

Consider the follow scenario.  In Windows 7, you create a new simple volume in Disk Management or DiskPart.exe on a non-removable disk.  If your Windows 7 system experiences a sudden power loss within a few minutes of volume creation, you may notice the volume you created before the power loss is inaccessible and is not assigned a drive letter when you power the system back on.

Additionally, in Disk Management the volume may not have a status (for example, "Healthy") or a file system type listed.  If you try to modify the volume in Disk Management, you may receive the following error message:

The operation failed to complete because the Disk Management console view is not up-to-date.  Refresh the view by using the refresh task.  If the problem persists close the Disk Management Console, then restart Disk Management or restart the computer.