If you are reporting from a Cube in SSRS and you want to drill through to another report you can set up actions just like any other drill through except one small change. The parameter you pass to the drill through report must be changed to Unique Name instead of value.
Go to the detailed report that you are drilling down to and right click on the datasets folder then select show hidden data sets so you can see the parameter dataset. In this query you will see the key under the parameter value. This is the unique value that the report needs to receive. Changing the parameter to unique name takes care of this issue.