Permalinks – Post Name breaks home page

For some reason I’ve been unable to use “Post Name” permalinks for the last couple of WP updates/versions. They used to work but now I get “too many redirects” if I enable the cleaner post name option. Strangely, other pages on the site seem to work but not the home page. The .htaccess file has the mod rewrite code, which I assume is why the other pages work. But unless I resort to Plain permalinks (i.e. domain.com/?p=123) the home page won’t load. Any suggestions?

Thanks,
Wm