I'm using the new WordPress 3.8 and I've noticed that when I leave the admin page open in a tab, and return later, I'm getting a random thing happening with the dashicon fonts used for the menu icons.
They all turn to squares, rather than the appropriate dashicon. Its as if the connection to the server that hosts the webfonts has been temporarily lost.
Interestingly, just moving my mouse over the sidebar area makes the squares transform into their appropriate dashicon font symbol.
Has anyone else experienced this?