Hallo Lutz,
Where do you store the backup?
How big is your .lrcat-file?
Do you tick "Test Integrity before backing up" and "Optimize catalog after backing up" ?
I have discovered lately that it take *forever* if I let LR write the backup file on a network volume rather than a locally plugged drive, so I lost patience with that.
Going back to my internal drive, then copying the backup over afterwards is my current choice. I am well aware that I run the risk of disk crash in between.
No real clue as of when I encountered this long delay in getting backup, somewhere after 4.3 and lrcat-file beyond 1.5 GB.
After hitting <Enter> on my Win7-system I also get another dialog box, where I can choose between 3 options Try Again / Choos different backup folder / Exit.
If that should have vanished with Win8 I'd consider it a bug.
Cornelia