Joomla! 02.05.18. K2 2.6.8
I get a blank page when I save items. Corrections in the text are saved, but not images. Changing the author are also being saved, although I also get a blank page when I save this change.
I can I save text into categories, but here I also get a blank page when I try to add a picture.
I've checked after login error. There is no error when the show error is high in configuration.
Neither FF, Chrome or IE shows JS error
All components and extensions are updated :huh:

Hi. A blank page indicates a PHP error. Set error reporting to maximum under Joomla! configuration to see the error.

As I wrote - it's already done, but no errors, neither front- or backend.
I've also validated the PHP files in template/html/com_k2/

Disable some content or K2 plugins and try again. You should see the error.

I can save both Joomla categories and articles with image via image and link

All articles and categories in Joomla library are deleted.
All K2 articles, K2 categories and modules are unpublished.
Button - Simple Image Gallery Pro unpublished
Content - Simple Image Gallery Pro (by JoomlaWorks) unpublished
K2 - Simple Image Gallery Pro unpublished
Simple Image Gallery Pro unpublished
template/html/com_k2/ is changes to template/html/_com_k2/ - does that make it disabled??

Everything the same - I can save categories with image in JCE Editor and changes in articles, but articles still return to a blank page

I've tried to reinstall K2, but it's still the same

If I uninstall K2 and install again (loose all content and extra fields) it works fine

Now the system finally showed an error/warning?
When I open a category og an item are the following:
Strict Standards: Declaration of JParameter::loadSetupFile() should be compatible with that of JRegistry::loadSetupFile() in /home/haugemc/public_html/test/libraries/joomla/html/parameter.php on line 512

No this is just a notice. You should see the error in the white screen when you click save. Anyway you can also go to "System Information" and to K2 information page to get some details regarding your system. Finally make a list of all K2 and content plugins installed in your site. Finally since it works fine after you uninstall you might have a permissions issue preventing the update to complete.