Checkout At Wincustomize Store

Is it just me or is there a problem with the Store. I Have tried to purchase a Master skin several times in the past few day's and I get this message? Any suggestions?

Server Error in '/' Application.
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Unable to cast object of type 'System.String' to type 'System.Security.Principal.IIdentity'.
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.InvalidCastException: Unable to cast object of type 'System.String' to type 'System.Security.Principal.IIdentity'.

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:


[InvalidCastException: Unable to cast object of type 'System.String' to type 'System.Security.Principal.IIdentity'.]
Page_Cart.ProcessCommands() +427
Page_Cart.Page_Load(Object sender, EventArgs e) +154
System.EventHandler.Invoke(Object sender, EventArgs e) +0
System.Web.UI.Control.OnLoad(EventArgs e) +99
System.Web.UI.Control.LoadRecursive() +47
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1061




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Version Information: Microsoft .NET Framework Version:2.0.50727.42; ASP.NET Version:2.0.50727.210