Backup gives me completion with error hresult 0x80042318
Whats the rest of the error? Did you have a chance to look into the logs?
My educated guess would be that you are having this issue on VSS snapshot creation.
Please edit the plan and check these two options: Force using VSS and Use system VSS provider.
After that please try re-registering VSS core components following these instructions:
1) Create new text document at any place you want
2) Paste following code into it:
net session >nul 2>&1
if %errorLevel% NEQ 0 (
echo Permissions are insufficient
echo Make sure to run this script with administrator privileges
set /p=Press ENTER to close
exit /b 1
REM echo on
REM enable string above for debugging only
cd /d %windir%\system32
net stop vss
net stop swprv
regsvr32 /s ole32.dll
regsvr32 /s oleaut32.dll
regsvr32 /s vss_ps.dll
regsvr32 /s /i swprv.dll
regsvr32 /s /i eventcls.dll
regsvr32 /s es.dll
regsvr32 /s stdprov.dll
regsvr32 /s vssui.dll
regsvr32 /s msxml.dll
regsvr32 /s msxml3.dll
regsvr32 /s msxml4.dll
net start swprv
net start vss
3) Please change the file extension from .txt to .bat
4) Execute this bat file and run the backup plan again.