IE8 .net 4.0 IIS6 “Ajax client-side framework failed to load”

Question

I just upgrated from VS2005 to VS2010 and works fine except for the following error on IE8 only:

User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; 
.NET CLR 1.1.4322; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; .NET CLR 
2.0.50727; yie8) Timestamp: Tue, 16 Aug 2011 18:46:04 UTC

Message: ASP.NET Ajax client-side framework failed to load.
Line: 130
Char: 34
Code: 0
URI: http://...

Message: 'Sys' is undefined
Line: 15
Char: 1

Seems like the the ScriptResource.axd js is not loaded correctly most of the time on this browser.

I've researched a lot about this kind of error and tried several things without luck. The wreird thing is that it's happenning just on IE8. Chrome and Firefox work fine. It also works fine sometimes on IE8 :S

Answer 1

I din't find a conventional solution for this problem. After debugging it I noticed that the problem was that the ajax script resources where loading after some other scripts.

I was not able to move the sripts up in the page because the application is very old and it wasn't even using master page, so I was limited on that. I researched about the script manager and I found a new property on asp.net 4.0 called EnableCdn that basically, if it's set to "true", it loads the resources from the Microsoft content resource servers. Doing that those scripts loads quicker and the errors disappeared.

I hope this experience be useful for someone else.

Thanks!