Yeah, this tends to happen when your stats reach a certain point. The formatting does go a bit haywire. There's no real fix for it on DSi, though it sometimes goes away temporarily after clicking through the game a few times (only to return when re-entering the game). This glitch is not present on most PC browsers, so you can play OverlorDS on a PC if it really gets to be a visual challenge.
I have that. It only goes away when my caffeine goes below 10,000 and comes back whenever it gets back above 10,000. I know it doesn't really matter, but does it happen with battery too?