Some time ago, during the Beta ages of Whidbey, I posted about trouble with the new ClickOnce technology. Now ClickOnce hit me again...

Having installed the RTM version of VS 2005, I was preparing a ClickOnce demo, and when I tried to install the simple WinForms app from the auto-generated PUBLISH.HTM within Internet Explorer - nothing happened. Nothing. No error message, no log entry.

I checked the HTTP traffic, which showed that the file was actually downloaded, and had the "application/x-ms-application" content type.

I checked the MIME association in Windows Explorer which showed that .application was associated with dfshim.dll.

I checked that dfshim.dll was loaded into the iexplore process.

I checked that I could install the app by launching the .application file from the file system via Windows Explorer.

I was going mad ... until I remembered s.th. about Onfolio...

During Whidbey Beta, I was using Onfolio 1.0, and it turned out that, in order to use it properly with a Beta of .NET Framework 2.0 installed, you had to put a iexplore.exe.config file in the IE directory, containing

<supportedRuntime version="v1.1.4322"/>

Well, guess what - that file was still there.

After renaming it, ClickOnce worked like a charm. And since Onfolio is fixed by now, it too does work.

I thought I'd tell you about this in case you come across a similar issue somewhere, some time. If so, look for the IE config file...