what is out of stock?

[Alemantico]

Dear people,
since this might be some of a simple config-error, I hope this time you can help me! But even after asking the www, I couldn't fetch a right solution yet;
Even all my products are in stock! Nevertheless, I got a vm error message, saying "product out of stock". What on earth is vm talking about?

[Alemantico]

ps: sorry, I accidently added the "templates.jpg ", and cannot remove it.