Visual Studio 2010 Reloads Microsoft.VisualStudio.IDE.ToolboxControlsInstaller,ToolboxInstallerPackage'{2C298B35-07DA-45F1-96A3-BE55D91C8D7A} Every Time

Symptom

When opening a forms designer on Visual Studio the following toolbox loads each time and it takes a long time by loading the toolbox with the following information.

Microsoft.VisualStudio.IDE.ToolboxControlsInstaller,ToolboxInstallerPackage'{2C298B35-07DA-45F1-96A3-BE55D91C8D7A}

Root Cause

When you installed a later version of Sliverlight SDK, it has corrupted some data in the older version of the SDK (it is rather complex matter that I fully do not, nor tired to, understand.)

Possible Solution:

There are various options on this, and the best discussion about this is at this URL:  But it appears that this is related to Silverlight SDK corrupting some data in the SDK based on this post.

There are other discussions on this post.

In my specific case, setting

HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\VisualStudio\10.0\Packages\{2c298b35-07da-45f1-96a3-be55d91c8d7a}\Toolbox\DefaultItems to 0

made it worse.  I cannot recommend this.

Instead try un-installing and re-installing the Sliverlight SDK in the order of versions to fix the toolbox issue. Namely remove 5.0 SDK and 4.0 SDK then install the 4.0 first then 5.0 if you are still (having to) coding with Sliverlight.

As with anything, approach your fix with a big caution when dealing with config issues like this. Have a good back-out plan like backing up the registry settings etc.

If you don't care so much about Silverlight...

Because of my situation for needing to go beyond Mac and PC audience I have to avoid using Silverlight so I do not need it. If you are on the same camp as I am, just blow away the key altogether.

HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\VisualStudio\10.0\Packages\{2c298b35-07da-45f1-96a3-be55d91c8d7a}

For Additional Insights,

You may want to read this article from Infragistics people about How Visual Studio 2010 Toolbox Works.