Hi,
That sounds very odd - UD doesn't have any hooks into that part of the admin area. So, my guess would be that your WP site is running very close to your web hosting's memory limit, and that the difference made by de-activating is that it brings you the other side of that limit. (Different pages use different amounts of memory, and it's possible that the media library uses more than others, by its nature).
If your hosting company can tell you where the PHP error log on your setup is, then you can read it and know for sure what the problem is - whatever it is, it'll be logged.
Best wishes,
David