Strange property expansion

Hi there,
I am experiencing a strange behaviour with webtest properties. It seems webtest knows the property and its value but in the steps they don't expand. I will include a debug console output to clarify this. The example prop ist #{heise.suchbegriff} which will get inserted literally in com.canoo.webtest.steps.form.SetInputField below:

[setInputField] DEBUG (com.canoo.webtest.ant.WebtestPropertyHelper) - Notifying listeners of properties expansion: #{heise.suchbegriff} -> gepardenforelle
[setInputField]  INFO (com.canoo.webtest.steps.Step) - >>>> Start Step: setInputField "Suchbegriff eingeben" (10/24)
[setInputField] DEBUG (com.canoo.webtest.util.FormUtil) - Looking for form with text field named "q"
[setInputField] DEBUG (com.canoo.webtest.util.FormUtil) - No given form or given form not suitable, trying others
[setInputField] DEBUG (com.canoo.webtest.util.FormUtil) - No current form or current form not suitable, trying others
[setInputField]  INFO (com.canoo.webtest.engine.WebClientContext) - Current form set to (action=/kiosk/suche/?sort=d)
[setInputField] DEBUG (com.canoo.webtest.steps.form.AbstractSetFieldStep) - Found matching form HtmlForm[<form id="kiosk_searchbox" action="/kiosk/suche/?sort=d" method="get" accept-charset="utf-8">]
[setInputField] DEBUG (com.canoo.webtest.steps.form.SetInputField) - Found 0 textarea field(s)
[setInputField] DEBUG (com.canoo.webtest.steps.form.AbstractSetFieldStep) - Considering element HtmlTextInput[<input type="text" name="q" value="" class="textfield">]
[setInputField] DEBUG (com.canoo.webtest.steps.form.AbstractSetFieldStep) - Found 1 field(s)
[setInputField]  INFO (com.canoo.webtest.steps.form.AbstractSetFieldStep) - Found 1 suitable fields, considering only the first one
[setInputField] DEBUG (com.canoo.webtest.steps.form.SetInputField) - Set text for HtmlTextInput[<input type="text" name="q" value="#{heise.suchbegriff}" class="textfield">] to value #{heise.suchbegriff}
[setInputField] DEBUG (com.canoo.webtest.steps.Step) - Completed Step: setInputField "Suchbegriff eingeben" (10/24)
[setInputField] DEBUG (com.canoo.webtest.steps.Step) - Step didn't produce results, no need to notifying listeners
[setInputField] DEBUG (com.canoo.webtest.steps.Step) - <<<< Successful Step: setInputField "Suchbegriff eingeben" (10/24)

I'm using webtest build R_1811 and JDK SE 6 Update 26, a recently finished project at a customer site worked like a charm but is unaccessible for now.
I'm really stuck, any help is appreciated.

Regards
Carsten