One possible reason is that the embedded resource is from a DLL that has a file system modification date in the future. When ASP.NET handles the WebResource.axd
request, it attempts to set the Last-Modified
HTTP header to the modification date of the DLL. However, HttpCachePolicy.SetLastModified
throws an exception if the date is later than the current system time.
Try to identify the DLL that contains the embedded resource, and reset its file system modification date to the current system time (or to a date in the past). To do this, you can start Command Prompt and use the following COPY command (as discussed by Raymond Chen):
COPY /B ABC.DLL +,,