Vista - BUG: Using 'Converter' in nested ItemsControl

I think there is a bug concerning 'Converters' when using nested
bindings. The example program in this solution should print the
following output:

1:1.1
2:2.1
2.2
3:3.1
3.2
3.3

The example program iterates through two levels. I only use a
converter for the second level. The converter doesn't convert
anything, but is used to illustrate the problem. The output that I
receive looks like:

1:1.1
2:
3:

I think this is a bug in WPF. Compile and run the example program and
you'll see what is wrong. Remove the 'Converter={...}' part from the
'TextBlock' and you'll see that everything works fine. Download the
complete example on
http://forums.microsoft.com/msdn/default.aspx?siteid=1

The correct link for the example project is http://home.ict.nl/~ramklein/Download/ExposeBug.zip.