Passing Parameters to Sub Reports in RDLC Under VS 2010

Question

Currently I'm working on a reporting website in VS 2010 using ASP.Net 4.0 and the 2010 RDLC designer. The report I'm building is similar to a Master-detail report, but I'm trying to do it with nested tables.

My issue is that I'm trying to pass a field value from my main report to a sub report. The table setup looks something like this:

2 Tables

First Table: [RecordID, Name, Date,] Second Table: [RecordID, Description, DueDate]

What I want to do is a table like this:

-------------------
|  Name  |  Date  |
------------------------------------
   |  Description1 |  DueDate      |
------------------------------------
   |  Description2 |  DueDate      |
------------------------------------
| Name2 | Date2 |
-----------------

With the entries for Description and DueDate bieng part of the sub report.

When I try to pass the RecordID in to the subreport as a parameter, which I have to manually define in the XML of the subreport because I can't find anywhere in the designer UI that will allow me to add report parameters to RDLC files, I get an error from the main report that says:

An error occurred during local report processing.
Value cannot be null. Parameter name: value 

So it appears to be erroring out before it ever reaches the point where it does the subreport loading.

I am getting data sent to the main report just fine, and if I remove the parameter from the subreport the data comes through. But if I add the parameter the report throws the error.

Does anyone have any ideas on what might be causing this?