ReportViewer RsInvalidItemPath Remote Mode

RS 2005 rsInvalidItemPath Error.

I am calling a drillthrough report from the ReportViewer control in a
VS 2005 web application. My report structure is as follows:


ParentReport (drillthrough)
ChildReport1(drillthrough)
ChildReport2


I can drill from Parent Report to Child1, but when I drill from Child1
to Child2, I get the following error:


The path of the item "(null)" is not valid. The path must be less than
260 characters long and must start with slash. Other restrictions
apply


Stack-Trace:
Microsoft.Reporting.WebForms.ReportServerException: The path of the
item "(null)" is not valid. The path must be less than 260 characters
long and must start with slash. Other restrictions apply.
(rsInvalidItemPath) at
Microsoft.Reporting.WebForms.ServerReport.PerformDrillthrough(String
drillthroughId, String& reportPath) at
Microsoft.Reporting.WebForms.ReportActionHandler.HandleDrillthrough(String
drillthroughID) at
Microsoft.Reporting.WebForms.ReportActionHandler.HandleAction(String
actionType, String actionParam, Int32& currentPage, Boolean&
pageSetByEvent, String& navigationID, String& searchText, Int32&
searchStartPage, String& alertMessage, Report& targetReport) at
Microsoft.Reporting.WebForms.ReportViewer.System.Web.UI.IPostBackEventHandl­er.RaisePostBackEvent(String
eventArgument)


Report Path: /screensave/screensave
Report URL: http://myserver/reportserver
IsDrillThrough: True


I am passing two parameters.


Just to add one more thing, when I run this from Report Manager which
is located on the same machine as the Report Server, I do not get this
error. It must be in the exchange between the reportviewer control on
the web app and the web service on the reportserver. Does anyone know
how this connection takes place in a drill down scenario? I assume
that when the web application (with reportviewer control) makes a call
to the web service, it opens the authenticated connection. Then at
each drill down event, does it make a round trip back to the web app?
It is on the third round trip that I see the error.


Thanks!