Frog CMS

Hy guys, I’m installing FrogCMS on a subfolder of a domain.
I named this subfolder “cms” so, the installation dir is “cms/install”.
When I try to submit the installation form, FrogCMS rise this error:

Warning: file_put_contents(../config.php) [function.file-put-contents]: failed to open stream: Permission denied in D:\inetpub\webs\caniledisavonait\cms\install\index.php on line 58

Fatal error: Class ‘PDO’ not found in D:\inetpub\webs\caniledisavonait\cms\install\index.php on line 75

obviously the file on “cms/config.php” is present and it has 777 permissions. I’ve also tried to re-upload all the cms files without success.

Edit: My Frog installationg is running on a Windows server. It seems that it has serious permission problems: I’ve tried to upload a local installation of FrogCMS and manually creating the database structure with sql exported from local phpmyadmin.
The CMS runs this way but if I try to upload some file trough the FileManager, it fails due to permission problems…. HEEEEEELLLPPP!!