4880 was indeed fixed but 4880 was about the admin language being included in the list?

Yes indeed,  which is spa-nl_NL. So it is still visible and included in the list?. 

And you have updated the theme selection plugin to the released version?

Yes, its 1.32.

Gosh, It looks like something has slipped through the testing net here. My apologies.
I will see what needs to be done and if something small and simple, post a solution here for you.
I am a little hampered at the moment as I have a broken development system (my SVN client has trashed some files and locked me out) but I will get onto it as soon as things are back to normal.

OK thanks and good luck with the broken system!

Back up and running at last…

Again – many apologies for missing this. If you want to make a small edit to correct it prior to the official update then… the file you need to edit is:

forum-plugins/user-selection/template-tags/sp-user-selection-tags.php

down at line 106 in this file you will find these two lines of code:

foreach ($langs as $lang) {
    $thislang = sp_filter_filename_save($lang);

We need to add a new line in between those two so it becomes:

foreach ($langs as $lang) {
    if(substr($lang, 0, 4) == 'spa-') continue;
    $thislang = sp_filter_filename_save($lang);

which will resolve your issue.

Thanks for the quick solution and it works fine now!

Excellent, Glad we got there in the end!