[XeTeX] xelatex and biblatex

[jadolov k]

Hi to everybody!I am trying to compile an article with a bibliography
formatted with Biblatex (a nice latex-based bibliographic system). It gives
me this error: every time when a citation occurs in the text, it gives an
underfull hbox problems on the whole line.
Is it a problem of biblatex? I could not understand that... I even tried to
modify the citation style I use, but without consequence.
Can someone help me?
Thanks
Artemio Keidan

P.S. source is attached
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://tug.org/pipermail/xetex/attachments/20080503/177759b0/attachment-0001.html 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: biblio.bib
Type: application/octet-stream
Size: 180859 bytes
Desc: not available
Url : http://tug.org/pipermail/xetex/attachments/20080503/177759b0/attachment-0001.obj 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Book.tex
Type: application/x-tex
Size: 8858 bytes
Desc: not available
Url : http://tug.org/pipermail/xetex/attachments/20080503/177759b0/attachment-0001.tex