Pango warning: "Invalid UTF-8 string"

[Matthias Kaeppler <nospam digitalraid com>]

Hi,

whenever I try to display strings in a TreeView 
which have German umlauts in it, they aren't 
rendered and I get a warning:
(duality.elf:4613): Pango-WARNING **: Invalid 
UTF-8 string passed to pango_layout_set_text()
The strings I display are std::stringS, but I also 
tried to construct Glib::ustringS from them 
without luck.
Any idea how I can get rid of these errors?

Regards,
Matthias