hi!
everything was working fine, I was starting to fall in love with my new addons (cb_conditionnals and cb_autoAction) ... until I got this error "Error decoding JSON data: Syntax error". So, when I unpublish the plugin "cb_conditionnals" my list of user'page is displayed ( visible in fronted) and as soon as I publish it, again the error !

thx for ur help;

So.

By testing various parameters of the plugin, I changed the access level of the plugin to "Registered" by default it was "public" and the error is gone.
it suits me because I did not understand the solution to which you send me above

Hi Krileon and many thx for ur reply,

everything works fine since I changed the "access level" parameter.
After reading your answer, i wanted to look a little more...ans i found a bug with a single member (administrator + registered),
even if there are several other members with these same rights, it's the only one that has this bug ( " Error decoding JSON data: Control character error, possibly incorrectly encoded" ).

So, I activate joomla error reports (max) and I have only one Notice "Notice: Constant K2_JVERSION already defined in /home/geaufrcujy/www/plugins/system/k2/k2.php on line 23"

and when I try to open the registration of the member concerned, I have a table that appears in the report (attachment):