Blank permalink page

I set up a new site, added in the theme then decided to upgrade to version 3.5 then I went to Settings->Permalink and the page is totally blank. Not sure if it was blank before the upgrade.

I deactivated all plugins, changed the theme to Twenty Eleven, Twenty Twelve – no change.

I tried various “fixes” in the WordPress forum which only made all sorts of weird errors and totally crashed the thing – I ended up re-uploading all the core files via ftp to get back to the backend this morning.

My hosting company says all the permissions are set correctly. Uses PHP v 5.3.2. I don’t know if it’s something I did wrong – hosting company says it’s a wrong setting in WordPress. Can you help?