Vista - one-way service operation not working

Hi! I'm trying to create a one-way service operation with no luck.
I've installed the Service Contract One Way Sample to see if it actually
works and I've found that the one-way operation works when the service is
hosted in a console application process but it doesn't work when hosted in
IIS; in this case the behaviour is not as expected because the client waits
for the service execution to complete.

Is this a known issue?? Any help?
Thanks in advance!