As there is little space left in partition C:, I run the following .bat script to clean the disk. After this, DNN sites didn't work any more.It shows the error as below:

Unhandled Error

Error Details

I searched the web and followed the search results tips to solve the problem, but the sites still didn't work.

Clean.bat file content:

@echo off

echo cleaning IE temporary folder...
del /f /s /q "%userprofile%\Local Settings\Temporary Internet Files\*.*"
del /f /s /q "%userprofile%\Local Settings\Temp\*.*"

echo cleaning system temporary files *.tmp *._tmp *.log *.chk *.old , waiting please...
del /f /s /q %systemdrive%\*.tmp
del /f /s /q %systemdrive%\*._mp
del /f /s /q %systemdrive%\*.log
del /f /s /q %systemdrive%\*.gid
del /f /s /q %systemdrive%\*.chk
del /f /s /q %systemdrive%\*.old

echo cleaning trash, backup files and pre-cached scripts...
del /f /s /q %systemdrive%\recycled\*.*
del /f /s /q %windir%\*.bak
del /f /s /q %windir%\prefetch\*.*
rd /s /q %windir%\temp & md %windir%\temp

echo pruging system useless cache files...
%windir%\system32\sfc.exe /purgecache

echo optimizing pre-read information...
%windir%\system32\defrag.exe %systemdrive% -b

echo Finished!

echo. & pause

Any help would be appreciated very much!

Your problem occurs with this line: rd /s /q %windir%\temp & md %windir%\temp

When you recreate the \windows\temp directory, it will not by default have modify (full?) permissions set for your NETWORK SERVICE account.  The NS account needs access to this directory in order to generate temporary serialization classes.  You'll have to re-add this permission manually as Ian outlined.

You really don't need to remove this directory, and should probably modify your batch file to just delete the files therein.

Hope this helps!

Brandon