HELP, Error with: Microsoft.Win32.UnsafeNativeMethods.CreateProcess in framework 1.1

Hi,

 Everyday when a lot of people is accessing to my site i retrieve the following error:

 Test Web:
MESSAGE: Referencia a objeto no establecida como instancia de un objeto.
SOURCE: System
FORM:
QUERYSTRING:

- Ocultar texto citado -
METHOD: Application_Error
STACKTRACE: at Microsoft.Win32.UnsafeNativeMethods.CreateProcess(String lpApplicationName, StringBuilder lpCommandLine, SECURITY_ATTRIBUTES lpProcessAttributes, SECURITY_ATTRIBUTES lpThreadAttributes, Boolean bInheritHandles, Int32 dwCreationFlags, HandleRef lpEnvironment, String lpCurrentDirectory, STARTUPINFO lpStartupInfo, PROCESS_INFORMATION lpProcessInformation) at System.CodeDom.Compiler.Executor.ExecWaitWithCaptureUnimpersonated(IntPtr userToken, String cmd, String currentDir, TempFileCollection tempFiles, String& outputName, String& errorName, String trueCmdLine) at System.CodeDom.Compiler.Executor.ExecWaitWithCapture(IntPtr userToken, String ...