Christophe,
> \onlySlide{1}{%
Use \onlySlide*
Further, prosper has its own mailinglist,
just as HA-prosper:
http://sourceforge.net/mail/?group_id=14812
http://listserv.surfnet.nl/archives/ha-prosper.html
and a wiki page:
http://wikiprosper.bbclone.de
Best,
-Hendri.