An exception occurred when trying to issue security token: Method is only supported if the user name parameter matches the user name in the current Windows Identity SharePoint 2010 FBA

You will see this error when you are using windowstokenroleprovider

<add applicationName="/" name="MyRoleProvider" type="System.Web.Security.WindowsTokenRoleProvider, System.Web, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" />

Change to sql role provider in your web.config file. check your central admin and

C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\WebServices\SecurityToken\web.config 

 files as well.

<add connectionStringName="SQLConnectionString" applicationName="/" description="Stores and retrieves roles from SQL Server" name="MyRoleProvider" type="System.Web.Security.SqlRoleProvider, System.Web, Version=2.0.3600.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" />