Microsoft Knowledge Base Article 918188 contains the following introduction:

After you perform a hardware or software restore of a disk, you may not be able to write or use the disk after you restart the computer. Before the restart, the Diskpart.exe utility either shows that the read-only flag values or that the hidden flag values are not set on the volume. After the restart, the Diskpart.exe utility either shows that the read-only flag values or the hidden flag values are set on the volume, or the utility shows that both flag values are set on the volume.

This problem may occur when one of the following conditions is true:

• A low-level restore of the data contains the attribute information.
• A hardware-level disk swap and the attribute flag values are set on the disk.