Today my entire school district was stricken by a worm. The symptoms involed:
loss of sound card in device manager
deletion of audio drivers
TCP/IP corruption
It’s been eating our network all week. I’m not sure how, but the bug was propogating via our network. To stop this, I’ve been imaging machines as I find them. Then I’d recreate [...]

This hack will automatically add the space required to include your mu admin bar. Add
body {padding-top: 28px !important;}
to the admin bar style and you are done.
Found in the source code of any wordpress.com blog!