This is what happens when you go to Alt+Tab while playing CS:S. I don't remember such problems before 23th June update.
...
https://www.youtube.com/watch?v=1zlEx5AZYw4
In celebration of "The Passing" release L4D2 devs played on public servers. I was lucky enough to join a game with L4D2_DEV_9 and play with him. Unfortunately i was sleepy as hell (waited whole night to have a chance to play with devs) and my ping really sucked (~600 ms) so i played really bad and managed to get smoked to death almost at the beginning and failed to save Coach at the ending.
...
https://www.youtube.com/watch?v=tsjOXSUmYQs