We’ve been experiencing the invalid webresource exception for at least a few weeks now, mainly on IE7 and IE8, although we’ve also seen it on IE9 and Firefox (but far less frequently).
2012-06-06 14:10:23,238  [admin] [xbqai0wdtzjrg2akwu0hjrc1] [(null)] ERROR Global - Unhandled exception was [System.Web.HttpException (0x80004005): This is an invalid webresource request.
2012-06-06 16:11:49,758  [(null)] [(null)] [(null)] ERROR Global - Application_Error : unhandled exception processing /[AppName]/WebResource.axd?d=Suu-bg3mCuf0dFdR6OaZkvX4qIzt-FMOe6pPRuU-iok0iBRX7G8SkmhJ6f6sVdRz5vgh3rhLmGeuyVCZQ7NlYAkluB8OomTcba5DZz_nqarySe1LWUgUVAdCHlVY9NrY1NCgWnu8yVgPuJfiygFy-Q2&t=634739782657507859
We fixed this by using fixed Machine Keys in IIS, and once all the users had deleted their Temporary Internet Files, we did not see the exception again. At least, until we deployed the latest build of our code onto the server.
Now, the issue is recurring fairly randomly and what happens is on certain pages our application, the selected menu item disappears as do the background images for RadTabStrips. What’s interesting is that it only happens on Internet Explorer (even 9), and if we open Developer Tools and check “Always refresh from server” under Cache, the problem goes away, but returns as soon as we uncheck that option.
We then went to our Temporary Internet Files folder and noticed that there are a number of files with names like: Telerik.Web.UI.WebResource.axd?compress=x&Telerik.Web.UI%2c+Version%3d2012.1.215.40%2c+Culture%3dneutral%2c …
We then opened all of these into Notepad and took the each of the problematic URLs in the error log to try and find the culprit, but to no avail.
We do have the following code on our Master page (if that helps):
<telerik:RadScriptManager ID="RadScriptManager" runat="server" EnableScriptGlobalization="true" EnablePageMethods="true" EnableScriptCombine="true">
We are unable to provide a sample of the issue, as we can’t reproduce it locally (other than with automatically generated keys).
Any advice you can provide would be greatly appreciated.