installing CI app on the subfolder of another CI app in my webserver

[eluser]n1colius[/eluser]
hi i have a problem regarding in installing CI app on the subfolder of my main app that also build in CI

so let's say my domain is www.mydomain.com and the app is in the root of my public_html folder. then i add another CI app that located in /public_html/demo/another_ciapp

i already change the base url config to http://www.mydomain.com/demo/another_ciapp/
but it's not working and it gives me this error

Code:

Warning: require(/home/nikoliu1/public_html/demo/ci-ajax-smtpmail/system//home/nikoliu1/public_htmldemo/ci-ajax-smtpmail/application/config/constants.php) [function.require]: failed to open stream: No such file or directory in /home/nikoliu1/public_html/demo/ci-ajax-smtpmail/system/codeigniter/CodeIgniter.php on line 52

Fatal error: require() [function.require]: Failed opening required '/home/nikoliu1/public_html/demo/ci-ajax-smtpmail/system//home/nikoliu1/public_htmldemo/ci-ajax-smtpmail/application/config/constants.php' (include_path='.:/usr/lib/php:/usr/local/lib/php') in /home/nikoliu1/public_html/demo/ci-ajax-smtpmail/system/codeigniter/CodeIgniter.php on line 52

any ideas how to fix this?