After more research I found this solution:
1. Go to the plugin and open qtranslate_javascript.php
2. Find the following code:
$q_config['js']['qtrans_wpActiveEditorOverload'] = "
jQuery('.wp-editor-wrap').unbind('mousedown');
jQuery('.wp-editor-wrap').mousedown(function(e){
wpActiveEditor = 'qtrans_textarea_'+this.id.slice(3, -5);
});
";
3. Replace this piece of code with:
$q_config['js']['qtrans_wpActiveEditorOverload'] = "
jQuery('.wp-editor-wrap').unbind('mousedown');
jQuery('.wp-editor-wrap').mousedown(function(e){
wpActiveEditor = 'qtrans_textarea_'+this.id.slice(3, -5);
var sliced = this.id.slice(3, -5);
if (sliced == 'content')
wpActiveEditor = 'qtrans_textarea_content';
else
wpActiveEditor = sliced;
});
";
But this bug should be fixed in the plugin