As we have discussed with you by email, we are unable to reproduce the error you had / are having with our support forums.
If you decide to go the child portals approach, do consider:
- all data will be isolated by portal. For instance,you will have 2 sets of users, one in each child portal. You will not be able to use the copy page to create a localized version of a page that exists in another language. When administering, you will have to log to each portal as each portal will have its own authentication. Also consider sitemap, etc.
- you will not have support for directing the user to a preferred language. You will probably be forced to have a landing page, where the user will select its preferred language. You will not have browser language detection, which would enable the user to be redirected to its preferred language on home page access.
Our localization extensions were actually built to avoid these limitations, by enabling 2 site branches inside the same portal. As for DNN 5.1.4 problems with enabled / disabled languages, I believe it can work OK once you have forced it to enable the proper languages, and use a valid portal default language.