Galleries not working

OK, so I just upgraded to 3.6.1 – mistake! Suddenly I can’t access my galleries. If viewed from the ‘outside’ all the images are there as they should be, but when I’m on the admin side there’s no sign of them. This means I cannot add to a gallery, change anything in it, or, in fact, do anything at all.

I’ve hunted high & low but to no avail.

And, no, I didn’t back up – duh moment! I also don’t know the first thing about codes.

Help! 🙂