I'm sure it's a bug, I get the same thing. It doesn't matter whether you zoom out or not; Once you zoom in, image scrolling stops working. If you attempt to scroll, the zoom control breaks.
There is a fix, though. Play some music. Load up an image, zoom in, and attempt to scroll. It'll break as usual. Hit the white button to display the music info, and hey presto, image viewing goes back to normal.
If you leave display mode, you have to repeat the process. Pressing the white button has no effect if there's no music playing. You don't have to leave the music info up once you've applied the "fix".
I've been meaning to file a bug report on this but I haven't had the time to check the current reports, make sure the latest builds aren't effected, check that it isn't a skin issue, etc...
There's also a problem where zooming in only shows you a low detail version of the image, and it's likewise fixed with that white button.