System.ArgumentException: Illegal characters in path.
   at System.Security.Permissions.FileIOPermission.EmulateFileIOPermissionChecks(String fullPath)
   at System.Security.Permissions.FileIOPermission.QuickDemand(FileIOPermissionAccess access, String fullPath, Boolean checkForDuplicates, Boolean needFullPath)
   at System.IO.FileInfo.Init(String fileName, Boolean checkHost)
   at System.IO.FileInfo..ctor(String fileName)
   at Diamax.Cms.Core.WebControls.BaseFileRetrieverHelper.WriteFile(String filename, HttpResponse Response)