For your situation, check the 'default' parameter values to see they haven't been assigned.

Mine have and is a 1-off.

I've read that in visual studio 05 there is a snap-in wrapper to control the properties of the Report Viewer...

Initially, I built my series of reports using Visual Studio with a Report Designer snap-in, where the parameters stopped the report viewer from generating the report - because I hadn't assigned default parameter properties.

But then switched to just developing within Report Builder and didn't use the menu concept until last night where I found the different behavior slide right passed the parameters because they had been assigned.

Thanks and good luck...