Re-add lost known issues.

refs: #10576, #10807, #9012

Commit 6a712dca was lost somehow,
probably in a buggy merge resolution.

wiki/src/support/known_issues.mdwn

@@ -551,3 +551,42 @@ GeForce GTX 960.
 
 This problem will likely be resolved once Tails
 [[!tails_ticket 10298 desc="includes a newer Linux kernel"]].
+
+Tor Browser does not support MPEG-4 videos
+------------------------------------------
+
+Tor Browser does not support MPEG-4 video streaming in Tails 2.0 and
+newer. Instead, in some cases you can download them and play them with
+the video player included in Tails.
+
+On the other hand, web sites that propose WebM video streaming work fine.
+
+See [[!tails_ticket 10835]] for more details.
+
+## Icons and information located on the top right corner of the screen are not displayed
+
+Sometimes, some of the icons located on the top right corner of the
+screen are not displayed entirely, or at all. For example, the Vidalia
+icon, or the icon that allows to change to another keyboard layout,
+may be hidden. Other information, such as the clock, may not
+be visible.
+
+Restarting Tails often solves this problem.
+
+See [[!tails_ticket 10576]] and [[!tails_ticket 10807]] for more details.
+
+## Network interfaces remain turned off
+
+For your safety, Tails blocks access to the network until you have
+chosen whether to
+[[spoof the MAC address|doc/first_steps/startup_options/mac_spoofing]].
+Once you have done that, network interfaces are turned on. However,
+since Tails 2.0, sometimes network interfaces remain turned off.
+
+If this happens to you, please
+[[report a bug|doc/first_steps/bug_reporting]]: we currently lack
+information to fix this problem.
+
+Restarting Tails generally solves this problem.
+
+See [[!tails_ticket 9012]] for more details.