>I also get sometimes "'_nonMSDOMBrowser' is undefined, again, referencing to WebResource.axd. So, this is the problem. The WebResource.axd does not get loaded. But, the code is there. Do you know whereelse I should look to find why this is happening?

Use Fiddler. That should tell you if
(a) the load request is made to the server
(b) whether it is found and downloaded