PowerView C2WTS Error

In trying to get PowerView working I'm receiving the following error: 

<detail><ErrorCode xmlns="http://www.microsoft.com/sql/reportingservices">rsCannotRetrieveModel</ErrorCode><HttpStatus xmlns="http://www.microsoft.com/sql/reportingservices">400</HttpStatus><Message xmlns="http://www.microsoft.com/sql/reportingservices">An error occurred while loading the model for the item or data source 'http://gig-portal-tst.ajga.com/sites/bicenter/PowerPivot Gallery/Wp_BusinessV1.xlsx'. Verify that the connection information is correct and that you have permissions to access the data source.</Message><HelpLink xmlns="http://www.microsoft.com/sql/reportingservices">http://go.microsoft.com/fwlink/?LinkId=20476&amp;EvtSrc=Microsoft.ReportingServices.Diagnostics.Utilities.ErrorStrings&amp;EvtID=rsCannotRetrieveModel&amp;ProdName=Microsoft%20SQL%20Server%20Reporting%20Services&amp;ProdVer=11.0.2100.60</HelpLink><ProductName xmlns="http://www.microsoft.com/sql/reportingservices">Microsoft SQL Server Reporting Services</ProductName><ProductVersion xmlns="http://www.microsoft.com/sql/reportingservices">11.0.2100.60</ProductVersion><ProductLocaleId xmlns="http://www.microsoft.com/sql/reportingservices">127</ProductLocaleId><OperatingSystem xmlns="http://www.microsoft.com/sql/reportingservices">OsIndependent</OperatingSystem><CountryLocaleId xmlns="http://www.microsoft.com/sql/reportingservices">1033</CountryLocaleId><MoreInformation xmlns="http://www.microsoft.com/sql/reportingservices"><Source>ReportingServicesLibrary</Source><Message msrs:ErrorCode="rsCannotRetrieveModel" msrs:HelpLink="http://go.microsoft.com/fwlink/?LinkId=20476&amp;EvtSrc=Microsoft.ReportingServices.Diagnostics.Utilities.ErrorStrings&amp;EvtID=rsCannotRetrieveModel&amp;ProdName=Microsoft%20SQL%20Server%20Reporting%20Services&amp;ProdVer=11.0.2100.60" xmlns:msrs="http://www.microsoft.com/sql/reportingservices">An error occurred while loading the model for the item or data source 'http://gig-portal-tst.ajga.com/sites/bicenter/PowerPivot Gallery/Wp_BusinessV1.xlsx'. Verify that the connection information is correct and that you have permissions to access the data source.</Message><MoreInformation><Source>Microsoft.ReportingServices.ProcessingCore</Source><Message msrs:ErrorCode="rsErrorImpersonatingUser" msrs:HelpLink="http://go.microsoft.com/fwlink/?LinkId=20476&amp;EvtSrc=Microsoft.ReportingServices.Diagnostics.Utilities.ErrorStrings&amp;EvtID=rsErrorImpersonatingUser&amp;ProdName=Microsoft%20SQL%20Server%20Reporting%20Services&amp;ProdVer=1.0" xmlns:msrs="http://www.microsoft.com/sql/reportingservices">Cannot impersonate user for data source 'TemporaryDataSource'.</Message><MoreInformation><Source>Microsoft.ReportingServices.ServiceRuntime</Source><Message msrs:ErrorCode="rsClaimsToWindowsTokenError" msrs:HelpLink="http://go.microsoft.com/fwlink/?LinkId=20476&amp;EvtSrc=Microsoft.ReportingServices.Diagnostics.Utilities.ErrorStrings&amp;EvtID=rsClaimsToWindowsTokenError&amp;ProdName=Microsoft%20SQL%20Server%20Reporting%20Services&amp;ProdVer=1.0" xmlns:msrs="http://www.microsoft.com/sql/reportingservices">Cannot convert claims identity to windows token.</Message><MoreInformation><Source></Source><Message>For more information about this error navigate to the report server on the local server machine, or enable remote errors</Message></MoreInformation></MoreInformation></MoreInformation></MoreInformation><Warnings xmlns="http://www.microsoft.com/sql/reportingservices" /></detail>

What's interesting is that PowerPivot works AOK.  The PowerPivot excel workbooks I've tried reside on the local SSAS instance, and the tabular ones are on another machine.  I've tried the constrained delegation fixes with no success, as well as using SQL Profiler haven't even seen the PowerView editor hit the SSAS instance at all.   I'm at a loss and was wondering if anyone had any ideas?

Thanks!