Thanks Erel...the problem seems to have disappeared (I hate it when that happens) but I'm not sure why. In any case...I upgraded to 5.2, did a 'clean files folder' and 'clean project' and all seems to be normal. Notwithstanding the panel loading thing I mentioned previously.
The thing I don't understand though is that on my laptop, all the image files are in the Files folder and can be viewed normally.
On my phone (HTC One X) the images are only in the virtual_assets folder and show a ! icon (in ES File Browser). If I try to view them using ES Image Browser then I get a 'Could not load image' view.
I don't quite have the B4A package structure in my brain yet but would I be right in assuming that images in virtual_assests appear corrupt because this is a protected location and the images get copied elsewhere when used by the app?
Thanks