Visual Studio 2012, Extension Updates, and (417) Expectation failed

While running Visual Studio 2012 behind a proxy, I received the following error message when checking for extension updates in the Visual Studio Gallery:

The remote server returned an unexpected response: (417) Expectation failed

A look around Google finally revealed a solution here:

http://www.jlpaonline.com/?p=176

Basically, he's saying the fix is to edit your devenv.exe.config file and change this:

<settings><ipv6 enabled="true"/></settings>

to this:

<settings><ipv6 enabled="true"/><servicePointManager expect100Continue="false"/></settings>

Thanks, Jeff!