RBloomberg error

I installed RBloomberg
(http://cran.r-project.org/src/contrib/Descriptions/RBloomberg.html)
sucessfully but when I want to run it, I get the follwong error:

 blpConnect()

Fehler in getClass(class(object)) : "BlpCOMConnect" is not a defined class

I use it at home with my bloomberg anywhere account installed on my
machine, Windows Vista and R 2.5.1.
Do I have to install anything else then Bloomberg Professional? Of
course I am logged in while I try to access BBG via the R package.

Thanks for any help/hints
Thomas