Vista - Custom Dependency Property in custom class hierarchy not workingcorrectly?!

Hi everybody,

I got a question on DPs. I want to provide 3 kinds of custom panels.
Each panel has functionality and properties which are in common so I
decided to implement a class hierarchy. On the base class (BasePanel)
I register two dependency properties and implement the concerning CLR
accessors. Now, I want to use a DataBinding in XAML on one of the
derived classes. I want to bind to an object of, let's say,
SpecialPanel1 --> there I want to bind to a DP which was introduced in
the base class. There are no compiler errors and the app is runniung but
nothing happens on the value of the DP:

BasePanel (with custom DPs)
|
|
--------------------------- .......
| |
SpecialPanel1 SpecialPanel2 ....... a.s.o.

in XAML:

<SpecialPanel1 DP_inherited_from_BasePanel={Binding .....} />

The value of DP_inherited_from_BasePanel is not touched! What's wrong?
I mean, Control also declares DPs which are used by derived classes ?!

Thanks a lot.
Chris