No pictures appear to select for sending!

Hi there. All works great with the app initially - my pc and iphone connect fine over the wireless network. However it doesn't seem to be working when it comes to getting the pictures up to select which ones to send from my phone to my pc. It says 'loading thumbnails' and there is the in-progress icon twirling away but I have left it more than half an hour several times, have come in and out of the app etc and no albums or images come up. I've tried through the desktop app and the web browser methods and neither work. I've probably got a couple of hundred pics on my camera roll but it says 'null' in the selected device album list. How long should it take for them to appear and is there any way you can advise on this? Thank you!