Language Detection only once per session

Not sure I follow. If you're using 'Path prefix with GeoIP detection fallback.' it will use the language from the path first. So using the language switcher block to load a URL with a different language code would take care of it. Right?

For my site, this is still a problem. I have 4 languages, and for the default language (english), there is no path prefix, but the other languages have a path prefix.

Basically, the outcome is that users in other countries who are redirected can never view the site in English.

I'm seeing this problem as well. Trying to find a solution now.

Maybe someone can check my logic here, but I did something like the following in the if block on line 109:

<?php
  // First check to see if a language was previously determined.
  if (isset($_SESSION['geoip_language']) && isset($languages[$_SESSION['geoip_language']])) {
    if (variable_get('geoip_debug', FALSE)) $_SESSION['geoip_language'] = NULL;
    return;
  }
?>

...And then changed the drupal_goto around line 140:

<?php

  // Now that the language is detected, do an absolute redirect to avoid page
  // caching in the wrong language.
  drupal_goto($language->path, NULL, NULL, 301);
  exit();
?>

This works perfectly for how I originally expected this module to work. I don't need this module to force the user into their detected language every time they visit the site, just send them to the appropriate home page on their first visit. I think the session is a good way to ensure than they aren't looped over and over again (especially if they want to see things in English).

If this works for others I'll submit a formal patch, but I'm thinking this might need to be configurable behavior, since some may prefer this module the way it worked before.