After updating to phpBB 3.1.0 or installing new one, when the board in opened from Chrome browser or Opera, the navbar is not showing well in RTL languages (Arabic here) as it's divided to 2 lines (image illustrating it in attachments).

A simple solution to this would be to open styles/prosilver/them/common.css, find:
.navbar

{ padding: 3px 10px; border-radius: 7px; }

Replace with:
.navbar

{ padding: 3px 10px; border-radius: 7px; white-space: nowrap; }