Check the protection on your DBM file(s). The file protection needs to be expressed in octal, not decimal.   dbmopen(%DB, "file", 666) ; should be   dbmopen(%DB, "file", 0666);

You might have been able to run this from the command line, but it'll create a file with funky protection bits. Since Apache is typicall run as a different user, they won't have access to the file.