We have a website that's using Microsoft Report Viewer 9 to consume reports from Reporting Services. We noticed an issue with the controls to set parameters losing their values.
We have a date control that's used to set a Start Date parameter for the report. When we use the date picker (calendar pop-up) to set the date, all dropdown lists whose values are dependent on the date picker will lose their values. The values may be available in the dropdown, they just do not remain selected. The report data being returned is correct though.
I should not that we have not seen this issue in Microsoft Report Viewer 10 while viewing the same reports.
After contacting Microsoft support, we believe this is an issue with Report Viewer, and that it has been resolved when using Visual Studio 2010.