asp.net – 什么可能导致一个服务器上的此错误,但不是另一个？

基本代码是这样的：

Try
    request = New ExternalWebService.ProcessRequestService

    ' Error occurs here:
    response = request.processCommand(parameters)

    ' Do some other stuff with response here

Catch webEx As System.Net.WebException

    ' This triggers and generic error gets displayed

Catch ex As Exception

Finally

End Try

使用SendFailure异常触发System.Net.WebException,并返回此堆栈跟踪：

The underlying connection was closed: An unexpected error occurred on a send. -
    at System.Web.Services.Protocols.WebClientProtocol.GetWebResponse(WebRequest request)
    at System.Web.Services.Protocols.HttpWebClientProtocol.GetWebResponse(WebRequest request)
    at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName,Object[] parameters)
    at ExternalWebService.ProcessRequestService.processCommand(parameters)

当我尝试在我的开发机器上调试此问题时,它工作正常,不会发生异常.

我们的网络服务器最近没有更新,我可以使用FireFox从Web服务器连接到wsdl服务(但我无法与IE连接,但这可能与我们在网络服务器上与IE有关的其他问题有关)

我已经尝试了为错误消息#2 here发布的所有解决方案,包括设置KeepAlive = False和ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3,但是没有人能解决这个问题.

我们的网络服务器运行Windows Server 2003和IIS6.0

什么可能导致这个错误发生在一台机器上,而不是另一台机器上？

编辑：这是跟踪信息：

System.Web.Services.Asmx Information: 0 : Calling XmlSerializer [Create XmlSerializer]
    Method: System.Xml.Serialization.XmlSerializer#1669721556::FromMappings(System.Xml.Serialization.XmlMapping[]#4002219=[4],ExternalWebService.ProcessRequestService#93032588=ExternalWebService.ProcessRequestService)
    Caller: System.Web.Services.Protocols.SoapClientType#42808772::.ctor(ExternalWebService.ProcessRequestService#93032588=ExternalWebService.ProcessRequestService)
    ProcessId=2796
    LogicalOperationStack=
    ThreadId=14
    DateTime=2012-12-21T17:02:39.2826250Z
    Timestamp=61755143048799345
System.Web.Services.Asmx Information: 0 : Return from XmlSerializer [Create XmlSerializer]
    Caller: System.Web.Services.Protocols.SoapClientType#42808772::.ctor(ExternalWebService.ProcessRequestService#93032588=ExternalWebService.ProcessRequestService)
    ProcessId=2796
    LogicalOperationStack=
    ThreadId=14
    DateTime=2012-12-21T17:02:39.6576250Z
    Timestamp=61755144323396760
System.Web.Services.Asmx Information: 0 : Calling XmlSerializer [Write Request]
    Method: Microsoft.Xml.Serialization.GeneratedAssembly.ArrayOfObjectSerializer#1231684::Serialize(System.Xml.XmlTextWriter#8023888=..,System.Object[]#19695157=[40],(null),(null))
    Caller: ExternalWebService.ProcessRequestService#60553900::Serialize()
    ProcessId=2796
    LogicalOperationStack=
    ThreadId=14
    DateTime=2012-12-21T17:02:39.7357500Z
    Timestamp=61755144598320131
System.Web.Services.Asmx Information: 0 : Return from XmlSerializer [Write Request]
    Caller: ExternalWebService.ProcessRequestService#60553900::Serialize()
    ProcessId=2796
    LogicalOperationStack=
    ThreadId=14
    DateTime=2012-12-21T17:02:39.7357500Z
    Timestamp=61755144621621529
System.Web.Services.Asmx Information: 0 : Calling WebRequest.GetResponse
    Method: System.Net.HttpWebRequest#2800407::GetResponse()
    Caller: ExternalWebService.ProcessRequestService#60553900::GetWebResponse()
    ProcessId=2796
    LogicalOperationStack=
    ThreadId=14
    DateTime=2012-12-21T17:02:39.7357500Z
    Timestamp=61755144622114240