htaccess

I wanted to change my permalink structure. I did so but it says that I need my .htaccess to be writable to complete the process. No problem I upload one with the correct rewrite text, but this breaks the site. Even if I upload a blank one, it breaks the site.

If I have the .htaccess so as to set the permalinks even that comes back not found. So I’m stuck in a loop. Site works OK without .htaccess but if i add one to complete the permalink change, everything is “Not Found” even the .htaccess. Confused. Thanks