Basic VSS Writer Troubleshooting
Launch an administrative command prompt and run 'vssadmin list writers' to determine which, if any, writers are in a failed state. Locate the writer in the list above, and restart the correlating service. Then rerun 'vssadmin list writers' to check if the writer is stable.
Restarting the services may not always resolve failed writers, and a reboot may be required.
If the writers continue to enter a failed state after stabilizing, further investigation will be required. Please include the System and Application event logs from the machine having issues when creating a case.