it will also fail if you have removed the .svn folders (although I dont know why you would do this)That Pre-Build Event tries to get the current revision and write it to a file.
Check if you:
- have Source\Core\Common\SubWCRev.exe
- have Source\Core\Common\Src\svnrev_template.h (and have at least reading permissions)
- have Source\Core\Common\Src\svnrev.h (with write permissions if you compiled at least once) or have write permissions to Source\Core\Common\Src at all (Vista and above might do that in some cases, depending on where your SVN Folder is)