Excessively slow script(s)
Fragment of a discussion from Support/LiquidThreads
It could be anything in the new jQuery release https://gerrit.wikimedia.org/r/#/c/16864/
Looks like you had already found the problem, but I tried to do the profiling you requested... http://toolserver.org/~nemobis/TWN-JS-firebug.tar.gz When Siebrand disabled ULS it went down from 18 s to 1 s (not related to LQT or anything else I could test). Firefox 14.0.1, fedora 17, AMD E350.