We are unable to create a restore point on our computer. In trying to do
so, we receive the error (also included as an attachment):

"The restore point could not be created for the following reason:
"The device is not connected. (0x8007048F)
"Please try again.

Subsequently, this problem is affecting our backup programs. In fact, this
problem became evident when our backup programs started aborting with errors
like "A shadow copy could not be created for the following reason:
Insufficient storage available to create either the shadow copy storage file
or other shadow copy data. (0x8004231F)" in Windows Vista Backup.

Initially, we thought there was a problem with the backup program. But then
we received similar errors from Norton Ghost and then discovered we could
not create a manual restore point without an error. As such, the backup
program problems seem only to be a symptom of the problem of not being able
to create a manual restore point.

Our drives are connected, we have plenty of free space on our hard drives
(50% or more), and we have no problem accessing our files or running our
programs. Yet, we cannot create a restore point from the System Properties
dialog (System Protection tab) without the error shown above indicating that
the device is not connected.

Any suggestions?