Input string was not in a correct format

I have install SSRS 2005 installation went fine. I was able to open report Manager and also deployed and opend some reports.I coverted over to Forms Authentication and now I get this Input string was not in a correct format error. See below:

Server Error in '/Reports' Application.

Input string was not in a correct format.

Description:An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details:System.FormatException: Input string was not in a correct format.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[FormatException: Input string was not in a correct format.] System.Text.StringBuilder.FormatError() +54 System.Text.StringBuilder.AppendFormat(IFormatProvider provider, String format, Object[] args) +2834788 System.String.Format(IFormatProvider provider, String format, Object[] args) +93 Microsoft.Samples.ReportingServices.CustomSecurity.UILogon.BtnLogon_Click(Object sender, EventArgs e) in T:\Program Files\Microsoft SQL Server\90\Samples\Reporting Services\Extension Samples\FormsAuthentication Sample\cs\FormsAuthentication\UILogon.aspx.cs:127 System.Web.UI.WebControls.Button.OnClick(EventArgs e) +105 System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +107 System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +7 System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +11 System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +33 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +5102

Can someone give me an idea of where I should look to correct this error.

Thanks!

[2518 byte] By [Charnata1] at [2007-12-23]