resolved: wipped everything and reinstall.

Hello everyone, I'm just beginning to take a look in the wonderful world of K2.
Given that in reality I have not of course to the end use of the additional fields of K2 (you in this regard, some guidelines to advise monkeys crazy newbie?), Now I find myself with a problem:
in the list to display all the items in the categories, I get this error:

Notice: Undefined property: stdClass::$imagenone in /htdocs/public/www/components/com_k2/helpers/utilities.php on line 151

I've installed new K.2.5.1 (error was in 2.5 also) with Joomla 1.7.2 . . .

The site is www.thema-med.com (if you want to give me some help I can give you in pm login and password)
looking on google I found nothing about this, have any suggestions?

As usual, sorry for my poor gtranslated english.
Thanks and have a nice day!