Please provide more detailed information, we need more info to find your problem...! If you can, attach a screenshot...
Maybe its a problem with your ROM, try running it in DeSmuME emulator. If the same problem exists, redownload the rom again from the main site. Or get the latest version of no$gba and try running the game in it.
Oops. I viewed on my mobile, couldn't see properly. Sorry. As Infernape said, try the latest version of DeSmuME, or if that doesn't work, try No$GBA 2.7a. If neither of those work, download a new ROM, patch it with the DS-Scene Rom Tool (there's a tutorial in the Tutorial board) and run it again.
Dude you should explian your problem, you shouldnt post just one small snapshot and let the others make guess what your problem is. That pic doesnt really explain much, you are supposed to explain when and at what locations it happens, or if it happens only in battle or in the overworld as well... Anyway try out the solutions mentioned. I saw the pic in my pc and still didnt notice the problem at first.
