I have pretty the same issue. My report is showing balances. And balances could be changed any time. So if i run report first time - it shows actual balances (2 lines in report). If then i'll change balances and run report second time - i see cached result (2 lines instead of 3, even if i see in debug mode that my sql query returns 3 records and send them to show into report).
I am using ReportViewer, latest version of Telerik reporting. I am using FileCache.
Any ideas how to fix it? I've tried to clear cache and session as suggested above - didn't help