If you want a snapshot report of today's inventory value, run Reports, Items, Value List report.
If you want the Inventory Valuation report to work correctly by date range, you need Cumulative Update 5 or higher installed (2.0.200x).
If CU5 is installed and results are not as expected, run MicrosoftFixit50537.msi. This was provided with Feature Pack 1 when the Inventory Valuation report was first added to RMS. The MSfixit populates the tables required for the report while CU5 fixes a bug in those tables. If you restore the RMS sample database, you must also run MSfixit before using the Inventory Valuation report. The report was broken at some point then fixed in CU5.
If you do not have CU5 installed and need inventory values for a historical date in time, you can run the Value List report for today, then run Item Movement Report with From date set to one day after the historical date and To date set to today. Summarize the report results by dept or category and apply those figures (+/-) against today's Value List report.