Firefox very slow with Visual Studio and Vista

Microsoft Visual Studio

Today I ran into a strange bug that saw me and another developer pulling our hair out, and reverting back to older and older code trying to work out when we introduced the bug.

The problem is this: we have a drag and drop desktop page that does an ajax call when a module is moved (it’s based on Jquery and Ajaxpro). It all worked fine a few days ago, and it worked fine on our test server that runs IIS, but in the local development environment (Visual Studio 2008 using its local web server) it runs really slow in Firefox3. Other browsers seem fine – we tested with Chrome, and IE7 with no problems.

After I managed to narrow down that the problem doesn’t occur once we publish the current code to an IIS box I started to do a little Google fu…

The problem was actually simple –  It looks like this is a problem with Firefox’s IPv6 setting. To fix it type About:config into the address bar in Firefox, Agree to the warning message, and then navigate to the net.dns.DisableIPv6 setting. Double click this setting to set it to true, and close the tab. That’s it! The problem should now be fixed.

Credit where credit is due – I found the fix here through my Google fu.

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