There seems to be a couple of issues listed for similiar issues but I just updated to 1.4.8 and still have this issue.

I have two of these in a directive to allow users to move items from one list to the other (both lists are subsets of a bigger list of items, and are filtered so no items can be in both lists).

<select id="multiSelectAvailable" 
ng-model="selected.available" 
multiple="multiple" 
size="{{available.length}}" 
ng-options="e as e[displayAttr] for e in available">
</select>

<select id="multiSelectSelected" 
ng-model="selected.current" 
multiple="multiple" 
size="{{model.length}}" 
ng-options="e as e[displayAttr] for e in model">
</select>

Sometimes when setting the list of items one or both of the selects becomes unresponsive. After changing the contents a couple of times it starts working again. However it could just be a coincidence.

** Edit **
Removed the comment about Swedish characters as that seems to not have an impact.