EasySocial Problems after Updating EasyBlog to 3.9.15275

This came to light in my other thread about SEF.
In order to keep things organised, I'm putting the details here.

Initially, I had problems with my main site after updating EB; I've since restored from backup prior to the update and that is functional again. I've also restored that backup into a dev version of the site and retraced my steps.

The symtpoms are:
Recent Updates page: profile menu in the ES bar works. Search opens the animated window but never completes.
On a user profile page: the dropdown profile menu doesn't work here. Clicking to send a Message doesn't work
By retracing my steps from the restored working version, this behaviour starts as soon as EB is updated to this version.

As it feels like a JQuery conflict, I started to disable and remove possible culprits:
JBolo - removed
Facebook Slider module: altered its parameter so it doesn't load JQuery
RokAjaxSearch - disabled
HotLogin: disabled
Optimiser: switched off defer Javascript option, then disabled
EasyBlog - purged cache

Also purged site cache at each step.

I'll hold off updating again for now on the live site, but I'm interested to know what might be causing this so that I can fix and update.

Thanks,
Steve