in the Permalink Settings i can only use the default setting, if i try to use a custom setting such as /%postname%/ all menu items send an “Error 404”
You will need to contact new host see if they have Mod_rewrite enabled as that Apache module that rewrites the urls using .htaccess file.
we did confirm the Mod_rewrite setting that you mentioned but it still only allows the default setting, when I try to use a custom setting such as /%postname%/ all the menu items still send an “Error 404”
if you using 3.3.1 there is new custom setting Post name did you try that.
no where can i find that “new custom setting Post name”
Try looking in Settings ->Permalinks.