I am using UpdraftPlus - Backup and Restore (free Version 1.9.45.1) with WordPress 4.1. I've found when I do a manual backup that I can't use the mouse to click on anything in the pop up window (UpdraftPlus - Perform a one time backup) that comes up after clicking on the Backup Now button. I was able to make a manual backup with the mouse before updating to WordPress 4.1. I have verified this problem on two web sites.
The highlight in the pop up window is on first check box (Don't include the database in the backup). I've found I can tab down to the Backup Now button and hit return to start the manual backup, so the problem is just with using the mouse in the pop up window. Small problem, but I expect you want that to work too.
Thanks, Keith