Page not found error when using panels I'm trying to add a block to an existing panel. The dialog opens but then I see this error, 


  The requested page "/panels/ajax/editor/select-content/panels_page_wizard:landing_page/bottom" could not be found.


and the ajax spinner never stops. The panel module is currently up to date, and google doesn't return any hits for the error.

I can create a brand new panel page, and the same problem occurs.
Turned on logging and saw Rejected-By-UrlScan next to the 404 errors.

Since our site is hosted in IIS, I needed to go into URLScan config, and allow colons, which are used by the Panels ajax func

C:\Windows\system32\inetsrv\urlscan\UrlScan.ini

; :   ; Don't allow alternate stream access