Shipping Method Problem..When click Next button, after selected shipping method display Error

Hi..  i am using your Nopcommerce 1.4 posted..It's nice to work..
but i added products to shopping cart then when i am clicking  shipping method displaying error in sometimes.. i put error in below ..so pl find out and give solution  for this error..

Exception of type 'System.Web.HttpUnhandledException' was thrown.
[The exception details for the log entry.] Exception:   System.Web.HttpUnhandledException: Exception of type 'System.Web.HttpUnhandledException' was thrown. ---> System.IO.FileNotFoundException: Could not find file 'C:\4833248\TEMP\btqupujx.dll'. File name: 'C:\4833248\TEMP\btqupujx.dll' at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath) at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy) at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share) at Microsoft.CSharp.CSharpCodeGenerator.FromFileBatch(CompilerParameters options, String[] fileNames) at Microsoft.CSharp.CSharpCodeGenerator.FromSourceBatch(CompilerParameters options, String[] sources) at Microsoft.CSharp.CSharpCodeGenerator.System.CodeDom.Compiler.ICodeCompiler.CompileAssemblyFromSourceBatch(CompilerParameters options, String[] sources) at System.CodeDom.Compiler.CodeDomProvider.CompileAssemblyFromSource(CompilerParameters options, String[] sources) at System.Xml.Serialization.Compiler.Compile(Assembly parent, String ns, XmlSerializerCompilerParameters xmlParameters, Evidence evidence) at System.Xml.Serialization.TempAssembly.GenerateAssembly(XmlMapping[] xmlMappings, Type[] types, String defaultNamespace, Evidence evidence, XmlSerializerCompilerParameters parameters, Assembly assembly, Hashtable assemblies) at System.Xml.Serialization.TempAssembly..ctor(XmlMapping[] xmlMappings, Type[] types, String defaultNamespace, String location, Evidence evidence) at System.Xml.Serialization.XmlSerializer.GenerateTempAssembly(XmlMapping xmlMapping, Type type, String defaultNamespace) at System.Xml.Serialization.XmlSerializer..ctor(Type type, String defaultNamespace) at System.Xml.Serialization.XmlSerializer..ctor(Type type) at NopSolutions.NopCommerce.BusinessLogic.CustomerManagement.Customer.set_LastShippingOption(ShippingOption value) in D:\GroceryXpert Source Code 27th March\Source Code\Libraries\Nop.BusinessLogic\Customer\Customer.cs:line 345 at NopSolutions.NopCommerce.Web.Modules.CheckoutShippingMethodControl.btnNextStep_Click(Object sender, EventArgs e) at System.Web.UI.WebControls.Button.OnClick(EventArgs e) at System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) at System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) at System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) --- End of inner exception stack trace --- at System.Web.UI.Page.HandleError(Exception e) 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.checkoutshippingmethod_aspx.ProcessRequest(HttpContext context) in c:\4833248\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files\root\70cecfa2\1ce479c4\App_Web_wkcvqrad.6.cs:line 0 at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)