Rodney I logged this in Gemini DNN-11497

Thanks for getting this to Gemini, which is looking all of a sudden very spiffy (thanks Joe?).

Is this a "re-createable" problem? That would sure go a long way towards testing/fixing. For me, I see it in a majority of event logs on various installations, and the tabs involved seem to be somewhat consistent on particular portals, but for the life of me I can't cause it to happen with any combination of OS or browser that I have tried.

But I think Rodney is right - check your logs and you might be surprised to see it happening to you too.

I'd like to know if my fix have any problem as well. 

What I did is load up the DNN source, find the break point, then add a if statement to make it only load the ajax when page is not postback.

with this fix,  the DNN module can not post data(HTML module) when Javascript disabled, because the DNN default module rely on ajax in order to work. But all my customised module can do postback without DNN errors when Javascript disabled.

The other thing is Telerik controls(RadMenu, RadPane), I don't think the Telerik control is a trouble maker. In fact, when I  using DNN521 default navigation and ActionList in container, it will cause another error when Javascript disabled.

I have also tried Javascript disabled on DNN 5.2.2 as well, works fine with default navigation and container.