Noticed that after 6.4.380 the gui is cut out in the "cogwheel" menu (see example: http://imgur.com/a/ce1jy).
I thought it could happen because of DPI settings in Windows but mine is set to DPI 100%.
It fixes itself if I hover over "Accounts and Vaults" which then expands the menu.
1Password Version: 6.4.380
Extension Version: 188.8.131.52
OS Version: Windows 8.1
Sync Type: 1Password Accounts