Can not read file, either file does not exist or there are permission problems

[baobosir]

moodle local onlinejudge using sandbox engine does not work. please help me! all onlinejudge produced the internal error info:Can not read file, either file does not exist or there are permission problems

[sunner]

Not a problem caused by ideone.com? Check PHP log please.

[baobosir]

line 174 of b/filestorage/stored_file.php: file_exception thrown

• line 192 of /local/onlinejudge/judgelib.php: call to stored_file->copy_content_to()