POST error

There is an error when try to submit a form:

Message: The state information is invalid for this page and might be corrupted.

UserAgent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; BTRS103066; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; InfoPath.1; .NET4.0C; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)
Referrer: http://192.168.1.254/surf.aspx?dec=1&url=uh4QwdELmPeTl8UN08UMm9ALtp4BvrbLmQR7wC07wAfKvT47sSBLv8V7wTbUB6X!
Error location: http://192.168.1.254/surf.aspx?dec=1&url=uh4QwdELmPeTl8UN08UMm9ALtp4BvrbLmQR7wC07wAfKvT47sSBLv8V7wTbUB6X!&method=POST
Http method: POST
Is authenticated: False
Is secure connection: False
Is local: False
dotNet Runtime: 4.0.30319.296
Server OS Version: Microsoft Windows NT 5.2.3790 Service Pack 2
Status code: 500 InternalServerError

Exception details: System.Web.HttpException (0x80004005): The state information is invalid for this page and might be corrupted. ---> System.Web.UI.ViewStateException: Invalid viewstate.
Client IP: 10.121.188.240
Port: 3259
Referer: http://192.168.1.254/surf.aspx?dec=1&url=uh4QwdELmPeTl8UN08UMm9ALtp4BvrbLmQR7wC07wAfKvT47sSBLv8V7wTbUB6X!
Path: /surf.aspx
User-Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; BTRS103066; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; InfoPath.1; .NET4.0C; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)
ViewState: 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... ---> System.ArgumentException: The serialized data is invalid. ---> System.IO.FileNotFoundException: Could not load file or assembly 'eTempo.Global, Version=5.4.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. El sistema no puede hallar el archivo especificado.
at System.RuntimeTypeHandle.GetTypeByName(String name, Boolean throwOnError, Boolean ignoreCase, Boolean reflectionOnly, StackCrawlMarkHandle stackMark, Boolean loadTypeFromPartialName, ObjectHandleOnStack type)
at System.RuntimeTypeHandle.GetTypeByName(String name, Boolean throwOnError, Boolean ignoreCase, Boolean reflectionOnly, StackCrawlMark& stackMark, Boolean loadTypeFromPartialName)
at System.RuntimeType.GetType(String typeName, Boolean throwOnError, Boolean ignoreCase, Boolean reflectionOnly, StackCrawlMark& stackMark)
at System.Type.GetType(String typeName, Boolean throwOnError)
at System.Web.UI.ObjectStateFormatter.DeserializeType(SerializerBinaryReader reader)
at System.Web.UI.ObjectStateFormatter.DeserializeValue(SerializerBinaryReader reader)
at System.Web.UI.ObjectStateFormatter.DeserializeValue(SerializerBinaryReader reader)
at System.Web.UI.ObjectStateFormatter.DeserializeValue(SerializerBinaryReader reader)
at System.Web.UI.ObjectStateFormatter.DeserializeValue(SerializerBinaryReader reader)
at System.Web.UI.ObjectStateFormatter.DeserializeValue(SerializerBinaryReader reader)
at System.Web.UI.ObjectStateFormatter.DeserializeValue(SerializerBinaryReader reader)
at System.Web.UI.ObjectStateFormatter.DeserializeValue(SerializerBinaryReader reader)
at System.Web.UI.ObjectStateFormatter.DeserializeValue(SerializerBinaryReader reader)
at System.Web.UI.ObjectStateFormatter.DeserializeValue(SerializerBinaryReader reader)
at System.Web.UI.ObjectStateFormatter.DeserializeValue(SerializerBinaryReader reader)
at System.Web.UI.ObjectStateFormatter.DeserializeValue(SerializerBinaryReader reader)
at System.Web.UI.ObjectStateFormatter.DeserializeValue(SerializerBinaryReader reader)
at System.Web.UI.ObjectStateFormatter.DeserializeValue(SerializerBinaryReader reader)
at System.Web.UI.ObjectStateFormatter.DeserializeValue(SerializerBinaryReader reader)
at System.Web.UI.ObjectStateFormatter.DeserializeValue(SerializerBinaryReader reader)
at System.Web.UI.ObjectStateFormatter.DeserializeValue(SerializerBinaryReader reader)
at System.Web.UI.ObjectStateFormatter.DeserializeValue(SerializerBinaryReader reader)
at System.Web.UI.ObjectStateFormatter.DeserializeValue(SerializerBinaryReader reader)
at System.Web.UI.ObjectStateFormatter.DeserializeValue(SerializerBinaryReader reader)
at System.Web.UI.ObjectStateFormatter.DeserializeValue(SerializerBinaryReader reader)
at System.Web.UI.ObjectStateFormatter.Deserialize(Stream inputStream)
--- End of inner exception stack trace ---
at System.Web.UI.ObjectStateFormatter.Deserialize(Stream inputStream)
at System.Web.UI.ObjectStateFormatter.Deserialize(String inputString)
at System.Web.UI.ObjectStateFormatter.System.Web.UI.IStateFormatter.Deserialize(String serializedState)
at System.Web.UI.Util.DeserializeWithAssert(IStateFormatter formatter, String serializedState)
at System.Web.UI.HiddenFieldPageStatePersister.Load()
--- End of inner exception stack trace ---
at System.Web.UI.ViewStateException.ThrowError(Exception inner, String persistedState, String errorPageMessage, Boolean macValidationError)
at System.Web.UI.ViewStateException.ThrowViewStateError(Exception inner, String persistedState)
at System.Web.UI.HiddenFieldPageStatePersister.Load()
at System.Web.UI.Page.LoadPageStateFromPersistenceMedium()
at System.Web.UI.Page.LoadAllState()
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
at System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
at System.Web.UI.Page.ProcessRequest()
at System.Web.UI.Page.ProcessRequestWithNoAssert(HttpContext context)
at System.Web.UI.Page.ProcessRequest(HttpContext context)
at ASP.surf_aspx.ProcessRequest(HttpContext context) in c:\WINDOWS\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files\root\9f36c96a\6859c4fe\App_Web_mypdky0t.0.cs:line 0
at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)