Reporting Services: there's data but it is not displayed in ReportViewer

I'm pretty new to Reporting Services though I have a lot of experience with Crystal Reports and databases (and MS Access reports if that counts ;-). Anyway, I created simple reporting project in VS2008 using wizard, with simple stored procedure that has 2 options parameters - and since they're optional I do not assign their values. There's 开发者_高级运维data in the dataset's "Preview data" window, but when I run the report it's empty - there're headers/etc but no data.

What can be wrong here? Can it be because I do not assign SP parameters - and if so, how do I do it? And how do I debug such cases "in general"? There's no even "preview" in report designer in VS2008.

Hm, I created report with tables inside, and manually added SP - it worked. But it shows data incorrectly in matrix. When I do the same thing using wizard in Report Builder 2.0 - it works like a charm - report is created, there's a preview, and data is correct in the resulting page. Looks like either VS2008 is broken or I don't understand something in there.