I hit the same problem, then fired up IE to try to get around it. Didn't work there either...unless you double click. I'd have given up if I'd not seen this comment!
The other thing that is rather confusing is that having selected the file, it's not clear how to proceed. I eventually clicked 'What have I missed' which seems to actually be 'I've not missed anything please click this button' - I think this could be better worded to just 'Go' or something similar once the file is selected.