cannot select profile for online event registration after upgrading civi on Joomla

(originally posted at http://civicrm.stackexchange.com/questions/7348/cannot-select-profile-for-online-event-registration-after-upgrading-civi-on-joom)

I've just upgraded CIVI on Joomla 3.4.1 from CiviCRM 4.5.3 to CiviCRM 4.6.9 and find that I can no longer select profiles to use for online event registrations when setting up an event.

I also find that when exporting participant records only the FIRST row of the exported csv file contains correct details for yes/no questions asked in existing custom data profiles. All following rows display numeric 1 or stay empty whereas first row correctly displays text "yes" or "no".

I could not replicate this issue on the demo joomla site, which is also Joomla 3.4.1 but running CiviCRM 4.6.0. I suspect the issue would appear on the demo site as well if it had a later version of civi.

I restored my website to pre-upgrade backup, then upgraded to CiviCRM 4.6.0. - This worked fine.

Then I did incremental upgrades of CIVI and all OK up to version 4.6.5 but when going from 4.6.5 to 4.6.6, the ability to select profiles and the odd behaviour with exporting participant data re-occurred.

I therefore suspect that code changes in civi 4.6.6 and onward cause this issue in Joomla installations.

I have found a similar issue that may or may not be relevant (but its too technical for me to be sure) https://issues.civicrm.org/jira/browse/CRM-15427

Is this a bug? if so how to progress it?