Win 8 Exception

3 posts, 0 answers
  1. Michael
    Michael avatar
    2 posts
    Member since:
    Jul 2014

    Posted 16 Jul 2014 Link to this post


    I just installed Fiddler 4 on Windows 8 and when I run it I get a NullReferenceException at Fiddler.frmViewer.DoPostInitPreLoad(). There is a screen shot attached. I've been using Fiddler for years and this is the first time I've ever had a problem like this. I Googled the error but nothing seems to match. I'm really not sure how to proceed.

    Any thoughts? Suggestions? 


  2. Michael
    Michael avatar
    2 posts
    Member since:
    Jul 2014

    Posted 16 Jul 2014 in reply to Michael Link to this post

    One other tidbit: I'm installing version but I noticed it installs in a Fiddler2 folder. Not sure if this is relevant.
  3. Eric Lawrence
    Eric Lawrence avatar
    832 posts

    Posted 16 Jul 2014 Link to this post

    Hi, Michael--

    First, thank you. I'm actually headed out on vacation tomorrow and if I didn't get your bug report today, I'd've been in big trouble.

    The problem you're reporting was indeed very recently introduced, and it only occurs on machines that have never run Fiddler before (or for which the registry settings had been obliterated). 

    I've fixed the problem in build, which you can find at

    With regard to your Fiddler2/Fiddler4 discrepancy-- this is expected. The only real difference between v2 and v4 is the version of the framework targeted; for historical reasons, "Fiddler2" is the value that you'll see in registry keys and file paths.

    Thanks again, and sorry for the inconvenience!

    Eric Lawrence

    Check out the Telerik Platform - the only platform that combines a rich set of UI tools with powerful cloud services to develop web, hybrid and native mobile apps.

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