Im currently running K2 v2.6.6 on Joomla 2.5.24.
As soon as I update K2 to 2.6.7 or 2.6.8, parts of my website no longer work.

Error message:
Notice: Trying to get property of non-object in /srv/www/sitemirror/components/com_k2/models/item.php on line 1347
Fatal error: Using $this when not in object context in /srv/www/sitemirror/components/com_k2/models/item.php on line 1560

item.php line 1560 shows:
$this->buildAliasBasedExtraFields($K2ItemExtraFieldsInstances[$item->id], $item);


Any ideas how to fix this?

Thanks,
Daniel

Hi. It looks like a third-party extension is using some K2 code in an incorrect way. Look for K2 extensions you might have ( plugins or modules ) and disable them temporarily until the error is gone.

You are right! It was the "K2 Related Content" Module from Effitech.
Now I have to find another module to show related articles...

Thanks,
Daniel

You should first check if there is an updated version of that extension.
You can also let the developer of that extension know about this so he can fix this.