My site is a multi-site configuration. It is now running but I will get a "not found" error on any single post or category. Pages are OK.
I checked the update had only been done on one theme Tiga when I looked the last change date in the server. However, I think this should not be the problem as I did try the old version as well as the default 2011 theme. None of them can make my site back to normal.
I also tried to re-install wordpress 3.4.2 but this did not solve our issue either.
We did have one issue when we run "update network", which put our website to maintenance mode. We followed the other posts to delete the file ".maintenance" from the server.
Please help to give some ideas how to solve this. My website: http://3wblog.net.
Thanks for the help!