Can't install any extension

I bought template 'Simplicity', but after installing I can't install a single extension. Tried everything: file permessions, changes in configuration script, reset ownership.. Someone could help me?

Do You get any errors? It seems like hosting specific problem.

Do You get any errors? It seems like hosting specific problem.

No, not a single error . After loading the page a few seconds, the browser returns to the 'upload and install' page.

What problem could be there with hosting?

The error is there, the problem is that this is ajax installation and warnings and errors doesnt show directly, bu they break installation.
display_errors = on in your php configuration is the problem.

How could I solve it? Add that line in my configuration.php?

In localhost everything is working fine, a little strange this.

You need to contact your hosting provider to ask how to disable display_errors in php config.
There is also a little "hack" in thread I have linked to, that makes possible installation to finish, but it doesnt have to work on every hosting company.