Getting error 1315 ("Forms authentication failed ...") on a new web server

I'm trying to get a new web server setup to use our ASP.NET 2.0 web sites.  When I run a SQL Server Reporting Services 2005 report on one of these web sites I get the following error message:
 
Log Name: Application Source: ASP.NET 2.0.50727.0 Date: 5/14/2012 2:16:30 PM Event ID: 1315 Task Category: Web Event Level: Information Keywords: Classic User: N/A Description: Event code: 4005 Event message: Forms authentication failed for the request. Reason: The ticket supplied was invalid. Event time: 5/14/2012 2:16:30 PM Event time (UTC): 5/14/2012 8:16:30 PM Event ID: 65b191e0bf8148098015715becbf3131 Event sequence: 2 Event occurrence: 1 Event detail code: 50201 Application information: Application domain: /LM/W3SVC/1/ROOT/ClientSystem-1-129815001904982049 Trust level: Full Application Virtual Path: /ClientSystem Application Path: D:\WebSites\ClientSystem\ ...