Hi everyone,
We've reverted MediaWiki from 1.20wmf11 to 1.20wmf10 in order to fix a problem with watchlists failing: https://bugzilla.wikimedia.org/show_bug.cgi?id=40103
The root cause of this problem is a compatibility issue with jQuery 1.7.2. We can't yet cleanly upgrade to jQuery 1.8. There are pending changes that might make this possible.
We may also try reverting all wikis to 1.20wmf10, and then moving forward with 1.20wmf12 on Monday. Still all TBD.
Rob