I have installed this, however I get a blank page when I goto 
http://admin.domain.tld/billing/ I even tryed chmod 0775 on the billing dir. any help??? following is the ls -la readout for the files
-rwxrwxr-x  1 vu2000 www-data  7951 Apr 19 00:39 adduser.php
-rwxrwxr-x  1 vu2000 www-data  2189 Apr 19 00:39 checklogin.php
drwxrwxr-x  2 vu2000 www-data  4096 Apr 19 00:39 clients
drwxrwxr-x  2 vu2000 www-data  4096 Apr 19 00:39 #CRON FILE
-rwxrwxr-x  1 vu2000 www-data  6383 Apr 19 00:39 delete_user.php
-rwxrwxr-x  1 vu2000 www-data  2606 Apr 19 00:39 download_invoice.php
-rwxrwxr-x  1 vu2000 www-data  7958 Apr 19 00:39 edit_user.php
-rwxrwxr-x  1 vu2000 www-data  4104 Apr 19 00:39 email_invoice.php
-rwxrwxr-x  1 vu2000 www-data  9188 Apr 19 00:39 email.php
-rwxrwxr-x  1 vu2000 www-data 12405 Apr 19 00:39 favicon.ico
-rwxrwxr-x  1 vu2000 www-data   452 Apr 19 00:39 _footer.php
-rwxrwxr-x  1 vu2000 www-data  2213 Apr 19 00:39 generate_report.php
-rwxrwxr-x  1 vu2000 www-data  2590 Apr 19 00:39 _header.php
drwxrwxr-x  4 vu2000 www-data  4096 Apr 19 00:39 includes
-rwxrwxr-x  1 vu2000 www-data  7880 Apr 19 00:39 index.php
drwxrwxr-x  2 vu2000 www-data  4096 Apr 19 00:39 #INSTRUCTIONS
drwxrwxr-x  2 vu2000 www-data  4096 Apr 19 00:39 languages
-rwxrwxr-x  1 vu2000 www-data  1356 Apr 19 00:39 login.php
-rwxrwxr-x  1 vu2000 www-data   409 Apr 19 00:39 logout.php
-rwxrwxr-x  1 vu2000 www-data  2972 Apr 19 00:39 _menu.php
-rwxrwxr-x  1 vu2000 www-data  9476 Apr 19 00:39 modify_client.php
-rwxrwxr-x  1 vu2000 www-data 18194 Apr 19 00:39 modify_invoice.php
-rwxrwxr-x  1 vu2000 www-data  8196 Apr 19 00:39 modify_item.php
-rwxrwxr-x  1 vu2000 www-data  6327 Apr 19 00:39 mypanel.php
-rwxrwxr-x  1 vu2000 www-data  9086 Apr 19 00:39 new_client.php
-rwxrwxr-x  1 vu2000 www-data 12506 Apr 19 00:39 new_invoice.php
-rwxrwxr-x  1 vu2000 www-data  8531 Apr 19 00:39 new_item.php
-rwxrwxr-x  1 vu2000 www-data  9322 Apr 19 00:39 new_payment.php
drwxrwxr-x  3 vu2000 www-data  4096 Apr 19 00:39 plugins
-rwxrwxr-x  1 vu2000 www-data  2877 Apr 19 00:39 reports.php
-rwxrwxr-x  1 vu2000 www-data 12645 Apr 19 00:39 sclient.php
-rwxrwxr-x  1 vu2000 www-data 15789 Apr 19 00:39 settings.php
-rwxrwxr-x  1 vu2000 www-data 11871 Apr 19 00:39 sinvoice.php
-rwxrwxr-x  1 vu2000 www-data 11991 Apr 19 00:39 sitems.php
-rwxrwxr-x  1 vu2000 www-data  9422 Apr 19 00:39 spayment.php
drwxrwxr-x  2 vu2000 www-data  4096 Apr 19 00:39 #SQL FILE
drwxrwxr-x  4 vu2000 www-data  4096 Apr 19 00:39 templates
-rwxrwxr-x  1 vu2000 www-data  6893 Apr 19 00:39 usermanager.php