dotnetnuke的bug？

不知道如何简要的描述这个问题，所以标题很笼统

错误重现方法：
首先安装好dotnetnuke，我将其安装到localhost/dnn313
login as  host
添加一个父站点
localhost/w1w2w3
登录localhost/w1w2w3 as host
转到 localhost/dnn313
此时不能被识别为host,认为未登录
登录 输入host/host 单击 登录
出现错误
Server Error in '/dnn313' Application.
Stack Trace:

[CryptographicException: 不正确的数据。
]
   System.Security.Cryptography.CryptoAPITransform._DecryptData(IntPtr hKey, Byte[] rgb, Int32 ib, Int32 cb, Boolean fDone) +0
   System.Security.Cryptography.CryptoAPITransform.TransformFinalBlock(Byte[] inputBuffer, Int32 inputOffset, Int32 inputCount) +805
   System.Security.Cryptography.CryptoStream.FlushFinalBlock() +40
   System.Web.Configuration.MachineKey.EncryptOrDecryptData(Boolean fEncrypt, Byte[] buf, Byte[] modifier, Int32 start, Int32 length) +139
   System.Web.Security.FormsAuthentication.Decrypt(String encryptedTicket) +114
   DotNetNuke.HttpModules.DNNMembershipModule.OnAuthenticateRequest(Object s, EventArgs e) +264
   System.Web.SyncEventExecutionStep.System.Web.HttpApplication+IExecutionStep.Execute() +60
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +87

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Version Information: Microsoft .NET Framework Version:1.1.4322.2032; ASP.NET Version:1.1.4322.2032

应该是cookies验证出错
两个站点使用了同一个cookies？？