I have noticed this behaviour before, if you open a document that was saved with WebView enabled you may get this message sometimes but it should work again if you disable/enable WebView. I don't know the reason why but I guess it may have something to do with temporary internet files.
If you are using the IE Plugin and HTTPS, that is likely to happen, because the Plugin uses its own ciphered protocol to communicate with the Server, and it does not use HTTPS. Is there any change this is what is happening?
I'm now having this same issue. I was working in web view and suddenly now I'm get the "Navigation to the webpage was canceled". I disabled then enabled WebView and still get the error message. I saved the document (QVW) not in webview, then reopened it and re-enabled webview and still get the message. I'm using the Desktop client V. 11.2 SR1 (64 bit) on a Windows 2008 server.
Does this mean my Document (QVW) might be corrupt possibly? (I hope not...)
I removed the sheet with the Heat Map extension and now my first sheet can go into webview again. I think something with that extension corrupted something. Might be the extension is not quite stable on QV 11.2 SR1.
i also had this sometimes together with extensions, when theres an error in the extension or the definition files for that, you could get this error in the WebView, but would also most likely get a js Error in AJAX Client.
The other thing is, that it happens often, when you just doubleclick on the QVW document in Windows Explorer.
I happens not so often, when you open the document from the Startpage within QliKVIew Desktop.