says "No question defined. "

How to reproduce this error:

1) Create a new question
2) Leave the XML blank
3) Save the question

You will get a PHP warning

warning: DOMDocument::loadXML() [domdocument.loadxml]: Empty string supplied as input in /drupal/sites/all/modules/closedquestion/question/FactoryQuestion.inc.php on line 85.
Problem loading question in node 1709

Karinaj, did you get any other errors?
I would expect an error from the XML parser, similar to what rekcor mentioned. If your installation has error reporting turned off you might have to look in the log files of your http server.

Ah, I just realised you're using a non-english translation of Drupal. In D7 the handling of translations changed, the port of ClosedQuestion doesn't deal with that yet, so apparently it's looking in the location of the English version.

The message "Notice: Undefined index: und" means the language is not set to the default ("und" means "undefined" I just found out)

I've updated the 7.x dev release that should fix it. Can you try that, once the build scripts have re-build it?
It also shows the language code the node uses, what does it list for you?

The build scripts on development builds run only every so often. You could try to apply the patch manually:
http://drupalcode.org/project/closedquestion.git/commitdiff/c5d6478?hp=3...

Just adding the following to the function closedquestion_load should give us enough information to see if it really is the problem:

$lang = $node->language;
drupal_set_message(t('Language = %lang', array('%lang'=>$lang)));

Explicitly setting it to English is different than leaving it undefined.

Ah, yes, another one.
In a few moments 7.x-2.0-beta2 should be on-line. Can you try that one?
It's an updated version with all the improvements of the 6.x-2.x branch. It does have one additional dependency, on the libraries module. http://drupal.org/project/libraries

It also needs some extra javascript libraries, but it also works if you don't install those on your own server. In that case it will use versions of a remote server.

I found one last reference to 'und', it's in lib/XmlLib.inc.php

Change line 108 from:

    $retval = check_markup(trim($retval), $drupal_node->body['und'][0]['format'], FALSE);

to:

    $lang = $drupal_node->language;
    $retval = check_markup(trim($retval), $drupal_node->body[$lang][0]['format'], FALSE);

You're welcome :)