Tuesday, 12 November 2013

Sudden fatal issues with .NET Framework 4 - "Faulting module name: clr.dll" - FIXED

One of the applications I built and deployed some time ago had been ticking over nicely for months, when suddenly the users reported that they were no longer able to access the application.

When trying to access it, they were getting 'Page cannot be displayed' errors - which meant their request was not even getting as far as starting their session in the application.

After rooting around, trying various things in IIS to no avail, I finally identified a Microsoft Hotfix which did the trick. Having cleared out the application logs in Event Viewer, I could see that the .NET framework was throwing errors in clr.dll.

Information on the Hotfix (and details of the specific errors which showed in the Event Viewer) available from this link:

However, you can't actually download the hotfix directly from there - I think because Microsoft are trying to encourage you to carefully review your situation versus their described issue, and for you to be extra cautious about installing it.

I decided that this hotfix had to be the only option I could take, other than trying to get some tailored (and expensive) support from Microsoft by supplying them with a dump of the logs etc, and I eventually found that the hotfix can be directly requested using this URL (for some reason I had to access the site using Google Chrome since IE was throwing JavaScript errors):

Within 5 minutes, the link to the hotfix had arrived in my email and I was able to download and install it.

It's worth noting that I stopped IIS (net stop w3svc) before applying the hotfix, which meant that I did not need to restart the remote server.

Now, the application seems to be back to normal. Well, let's see what the users tell me tomorrow.

Note: As usual, I have to declare myself free of blame if you install this hotfix and it doesn't work or causes any issues for you! :)