jQuery doesn't override in 6.15

I just noticed that jQuery that is included in my drupal installation is the original one from the /misc folder rather than from sites/all/modules/jquery_update. I have jQuery Update 6.x.-2.x-dev installed (tried uninstalling and reinstalling). No caching, theme rebuilt on every request. It used to work a few months ago, and the only significant thing that I can think of is the update to 6.15.

Any ideas on what might be wrong?

Thanks,
Andrey.