I get "error messages disabled" during phpThumb thumbnail creation

This error means,
that you have a wrong/bad folder path or folder permissions problem
 e.g.
- you web server document root was not detected properly
- your joomla folder path has invalid / bad characters , e.g. it starts with number
- you have set a bad path in image field configuration
- you haved deleted or renamed the images / thumbnail folder or it is not accessible due to wrong permissions / wrong ownership of folder
- you are access Joomla using a unix account alias syntax (~username), this may not work with phpThumb default configuration

-- To get more information on the phpThumb error message
(and make the real error message appear)
1. in file components/com_flexicontent/libraries/phpThumb/phpThumb.config.php
change line:
$PHPTHUMB_CONFIG['disable_debug'] = true;
to
$PHPTHUMB_CONFIG['disable_debug'] = false;

2. revisit the page that contains the error,

3. check if the error is now shown,
NOTE: if the error is not shown, then right click on the image thumbnail and
- copy the thumbnail URL
- then paste it into the address bar and open it

4. review the error message (search for word "error"), to find the reason and correct the problem

5. set disable_debug back to true