Error messages coming from untranslatable strings

Hi,
This is a site that is designed to operate in English, French, Arabic, Swahili and Spanish
http://www.refugeeresearch.net/

Since upgrading from 6 to 7, (and doing the i18n upgrade instructions fully) there appear to be a number of strings which are in the system in English that are just not translatable, while similar ones of the same type are.

One example is the titles of blocks. Some (such as "Navigation") translate fine. But others (such as "RRN Blogs") do not.

When I try to translate one of the untranslatable ones, I get what looks like the appropriate screen but an unable to type in the field. And if I press enter I get these messages:

Notice: Undefined index: strings in i18n_string_translate_page_form_submit() (line 213 of /var/www/sites/all/modules/i18n/i18n_string/i18n_string.pages.inc).
Warning: Invalid argument supplied for foreach() in i18n_string_translate_page_form_submit() (line 213 of /var/www/sites/all/modules/i18n/i18n_string/i18n_string.pages.inc).

When poedit files are imported, the strings don't translate even though I can see them in the posedit file.

Also: On the translation interface overview page, there are four columns without headers.

Thanks for any help.