web服务发生错误 System.IO.FileNotFoundException 解决办法

这几天framework 自动更新
结果造成webservices调用报错:

System.IO.FileNotFoundException:   找不到文件或程序集名称“ygbe1ssc.dll”，或找不到它的一个依赖项。  
  文件名:   “ygbe1ssc.dll”  
        at   System.Reflection.Assembly.nLoad(AssemblyName   fileName,   String   codeBase,   Boolean   isStringized,   Evidence   assemblySecurity,   Boolean   throwOnFileNotFound,   Assembly   locationHint,   StackCrawlMark&   stackMark)  
        at   System.Reflection.Assembly.InternalLoad(AssemblyName   assemblyRef,   Boolean   stringized,   Evidence   assemblySecurity,   StackCrawlMark&   stackMark)  
        at   System.Reflection.Assembly.Load(AssemblyName   assemblyRef,   Evidence   assemblySecurity)  
        at   System.CodeDom.Compiler.CompilerResults.get_CompiledAssembly()  
        at   System.CodeDom.Compiler.CompilerResults.get_CompiledAssembly()  
        at   System.Xml.Serialization.Compiler.Compile()  
        at   System.Xml.Serialization.TempAssembly..ctor(XmlMapping[]   xmlMappings)  
        at   System.Xml.Serialization.XmlSerializer.FromMappings(XmlMapping[]   mappings)  
        at   System.Web.Services.Protocols.XmlReturn.GetInitializers(LogicalMethodInfo[]   methodInfos)  
        at   System.Web.Services.Protocols.XmlReturnWriter.GetInitializers(LogicalMethodInfo[]   methodInfos)  
        at   System.Web.Services.Protocols.MimeFormatter.GetInitializers(Type   type,   LogicalMethodInfo[]   methodInfos)  
        at   System.Web.Services.Protocols.HttpServerType..ctor(Type   type)  
        at   System.Web.Services.Protocols.HttpServerProtocol.Initialize()  
        at   System.Web.Services.Protocols.ServerProtocolFactory.Create(Type   type,   HttpContext   context,   HttpRequest   request,   HttpResponse   response,   Boolean&   abortProcessing)  

google 到微软的解决办法：
http://support.microsoft.com/?id=823196

说是TEMP文件夹权限问题
提供了一个实用的跟踪办法，详见上面的连接：
 <system.diagnostics>
         <switches>
            <add name="XmlSerialization.Compilation" value="4"/>
         </switches>
    </system.diagnostics>

但是对我们的服务器无效，最后发现是CSC.EXE被破坏的原因
%system%\Microsoft.NET\Framework\v2.0.50727\csc.exe 文件修改日期为今天，大小为0
复制正常文件替换解决问题

不知道有没有类似自动升级造成的情况
或者是我们服务器被病毒破坏了？