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An update was released for Dapper on 21 August 2006 UTC, which has been found to cause problems on certain systems.

A subsequent update published 17 hours later corrects this, so if your system is fully up to date now and you have no obvious graphical system failures, then you are highly unlikely to be affected. However, delays to the system of update distribution mean that you should make sure you have fully updated before rebooting your computer. You can read more about the issue to ensure you will not be affected, and learn what steps we are taking to ensure this does not happen again.

If you have been infected, you can follow the instructions here. However, these instructions require an active internet connection.

If you want to fix this problem without an internet connection, you can do so if you have a removable storage device, such as for example your MP3 player. To do so, just follow the instructions here but instead of step 6, you download the file manually. You can then install it using sudo dpkg -i /path/to/xserver-xorg-core.deb. You can then follow the rest of the instructions.