I have never backed up my catalog - yes, you heard right. Every time I try, it's going on 2 hours or so and I finally cancel out. I have a ton of photos, so not sure if that's the problem, but it's frustrating and I don't know if this is normal. It gets to about 3/4 complete and then hangs.
I want to move from LR 5.7 to CC, which is why I want to make sure I have a good back-up, but not sure what to do.
To backup the LR catalog file just make a copy of it on an external drive. The catalog backup does not copy any images. You should do that yourself by copying all your images to an external drive.
The problem you are having probably has something to do with folder permissions.
How large is the catalog file (Not your images)?