DNN 7.1.1
I get this error from the register page and the Portal alias part of the site admin module. Seems to be the Telerik.Web.UI.WebResource.axd. Everything else appears to work fine.

I beleive it may have something to do with some custom rewrite rules to hise the subdirectory DNN is installed in on the server, though I've excepted .axd calls from the rules.

Also, the rules are done in IIS URL Rewrite, not from DNN, itself. I also can't seem to find any definative information on exactly how the new Advanced Friendly URL works. Mine install automatically strips the "www." from the url, no matter what alias I have set as default, for example...