"File is empty. Please upload something more substantial."

I’ve made a fresh wordpress install, upload my content to wp-content folder and then tried to import my posts and page through import tool with an XML file.

Can’t import any XML to wordpress trough import tool. It gives constantly this error, even uploading 4MB files when the limit is 10MB!
“File is empty. Please upload something more substantial. This error could also be caused by uploads being disabled in your php.ini or by post_max_size being defined as smaller than upload_max_filesize in php.ini.”

After some tries it imported my file but then redirect me to wp-admin/install.php in loop…I couldn’t access anymore to my site…is this some kind of bug?I’ve imported XML files to wordpress before without any problems..

Now what? If I answer in the install screen it says that wordpress is already installed and they redirects me again to install.php…