[SOLVED] Unable to create new user accounts in front end following upgrade of CB1.9 - 2.0

Joomla! 3.6.4
CB 2.0.15
CBSubs 4.1.0+build.2016.08.21.18.17.25.590769336

When I try to create a new user account (Test) I get the following error after clicking on the 'Submit' button:

"Error
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '(, , ) VALUES (547, 7, 1), (547, 28, 1), (547, 8, 1), (547, 29, 1), (547, 12, 1)' at line 1 SQL=INSERT INTO (, , ) VALUES (547, 7, 1), (547, 28, 1), (547, 8, 1), (547, 29, 1), (547, 12, 1), (547, 16, 1)"

The new user account appears in the Joomla - Users list but not in the CB Users list at this point.

Running CB Tools - Sync Users returns the following message:

"Added 1 new entries to Community Builder from users Table.
Joomla User Table and Joomla Community Builder User Table now in sync!"

The new user account now appears in both the Joomla and CB User lists.

When I try to delete the Test user account using CB User Management I get the following error:

"Error
Cannot delete row id 547 because: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'WHERE = 547' at line 1 SQL=DELETE FROM WHERE = 547"

CB Tools - Sync Users returns the following message:

"Removing 1 entries from Community Builder missing in users Table.
Joomla User Table and Joomla Community Builder User Table now in sync!"

The Test user account is now deleted from the user lists.

I can give you SuperUser access if you need it.

Thanks,

Phil.

The error looks cut short or modified. Please provide the full query error so I can see what table it is coming from. It does not look like it's coming from CBs. You may have a 3rd party CB or Joomla system plugin installed doing it. Try disabling non-core CB and Joomla system plugins 1 by 1 to see if issue goes away. Note CB 1.x to CB 2.x is not an upgrade, but a migration.

[SOLVED]

After disabling non-essential plugins one at a time I discovered that the problem was being caused by the System plugin 'Auto Subscription for Kunena v2.5-2 by Viktor Vogel'. This plugin only works with Kunena v2. I had updated Kunena to v5 at the same time as migrating my Joomla system from J2 to J3.6.5 and CB to the latest version when this problem appeared. Disabling Auto Subscription for Kunena appears to have cured the problem.

Phil.