They are broken and you won't get them back.
You can use the 'export messages' button to save them, that's about as much as you can do.
Use the search button.
I am also having this issue, no im not trying to open a sent message, im trying to view my old sent messages list so i can delete them... but i cant even get to that point, as soon as i press "sent messages" in my control panel it gives me the box like the OP had...
(10-18-2012, 04:39 AM)Zukeenee Wrote: Try clicking on the "Empty Folders" button on the top bar in your PM section. From there, tick the box next to "Sent Items" and click "Delete".