Unable to click "Add" in exclusions - build 6525

Hi,

I'm sure I am doing something wrong, but I wanted to add a folder to the exclusions of one of my backups. On the exclusion tab, I could see existing defaults there, and tried to follow suit.

There was no Browse button, which threw me, but there was an Add button. So I tried to add in C:\Users\Sco\Documents\my games. This was copied exactly from Windows Explorer, and was similar in format to the defaults. However, the Add button was greyed out. I tried typing it in manually, and noticed that it is active for the C character, yet once I get to : it then greys out. I tried surrounding in quote marks to no avail. I also tried simpler folders and files to no avail at all.

Am I missing something obvious, and how come I cannot see a browse button that I have seen on images on forums?

Many thanks,

Scott