When I click the Extra Fields tab on the 'Add/Edit Item' screen, the following warning is prompted:

Warning: Invalid argument supplied for foreach() in [path_to]\administrator\components\com_k2\views\item\tmpl\default.php on line 270

Environment: Apache 2.2.11, PHP 5.2.9-2, MySQL 5.1.33, Joomla! 1.5.11, Firefox 3.5 RC2, WampServer 2.0h

Hi Tamás!
This bug accours, when you start with blank installation of K2. There are NO extrafields in database.
Dev team work on it - in final code resolve this, hope. :)

Hi, Tibor!

I tested more, and I noticed the following with a clean install with the below steps:

1) I added an extra field group
2) i added some extra fields
3) I added a category
4) I opened the Add/Edit Item screen
5) I switched to the Extra Field tab and the error message mentioned in my starting post appeared.

So, it is not true, that this error persists without no extra fields :)

The following info regarding this issue may be interesting for the dev team :)

When I selected the category in the 'Details' section on the right, the error message disappeared and the "This category doesn't have assigned extra fields" information was displayed.

Fixed in v2 final. Thanks for reporting this issue to us.