Q: Constantly getting "Loading toolbox content from package" in Visual Studio AND IT TAKES FOREVER! Does anyone else have this problem?
The full message in the status bar says, 

Loading toolbox content from package 'Microsoft.VisualStudio.IDE.ToolboxControlsInstaller.ToolboxInstallerPackage' {D766DAA8-F81E-4621-9184-F21C7F389796}

This usually happens whenever I open a xaml file and VS sits there, unresponsive, for about 2 minutes.

A: This usually happens when opening the Toolbox (CTRL-ALT-X), or moving the mouse over the Toolbox icon (which appears on the left).
According to this Connect issue report, there's a workaround to be done, which may fix the issue: 
He said he simply removed the registry key under:
[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\
   VisualStudio\10.0\Packages\{D766DAA8-F81E-4621-9184-F21C7F389796} 

and the problem went away. Read more on that link.


*

*Be sure to take a backup of whatever registry changes you make!


A: I was facing the same problem and also tried to solve it by deleting to registry key(s). But the problem returned after a while.
The keys where back again.
But, I found at each key has settings for toolbox with the value 1, like:
...{2c298b35-07da-45f1-96a3-be55d91c8d7a}\Toolbox]
"Default Items"=dword:00000001

You can find this setting in the C:\Program Files (x86)\Microsoft Visual Studio 10.0\Common7\IDE\ShellExtensions\Platform\BaseConfig.pkgdef, line 8395. 
I changed the value from 1 to 0 ("Default Items"=dword:00000000) in all {2c298b35-07da-45f1-96a3-be55d91c8d7a}-keys and the file mentioned before.
The problem seems to be fixed, since over two weeks. The fix before worked less than one day.

A: *

*Start Visual Studio 2010 commandprompt

*type in  devenv.exe /log "c:\Users\\Desktop\vslog.txt"

*Just work normally in your visual studio 2010.

*after your work close visual studio and check the log file (vslog.txt)

*Search for "package load took" or "2C298B35-07DA-45F1-96A3-BE55D91C8D7A"


You might then find something like this:
  <entry>
    <record>574</record>
    <time>2012/09/14 07:36:45.386</time>
    <type>Information</type>
    <source>VisualStudio</source>
    <description>Toolbox: package load took 0 ms, ResetDefaults call took 12230 ms</description>
    <guid>{2C298B35-07DA-45F1-96A3-BE55D91C8D7A}</guid>
  </entry>

Now you can search the registry key and delete it (make sure VS2010 is closed).
[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\VisualStudio\10.0\Packages{2‌​c298b35-07da-45f1-96a3-be55d91c8d7a}] 

Maybe you will see other clues to your problem in the log file.
Make sure you BACKUP the registry or any other settings you make.
Learn more about visual studio switches:
http://msdn.microsoft.com/en-us/library/xee0c8y7(VS.100).aspx
The bug report on Microsoft Connect: http://connect.microsoft.com/VisualStudio/feedback/details/735555/silverlight-5-tools-bug-loading-toolbox-content-from-package-microsoft-visualstudio-ied-toolboxcontrolsinstaller-toolboxinstallerpackage-2c298b35-07da-45f1-96a3-be55d91c8d7a 
extra info: http://michaelcrump.net/fixing-a-broken-toolbox-in-visual-studio-2010-sp1

A: I had the same issue. I started VS with logging enabled as explained here. Once VS had started and froze on attempting to load the toolbox, I read the log file. I searched for "Warning" and the first entry was the following.
<entry>
    <record>39</record>
    <time>2013/03/07 22:30:32.671</time>
    <type>Warning</type>
    <source>VisualStudio</source>
    <description>The CTM file is out of date and should be deleted and rebuilt, but the file &apos;C:\ProgramData\Microsoft\VisualStudio\10.0\1033\devenv.CTM&apos; could not be deleted.</description>
</entry>

I ran VS as administrator, waited until it locked up. I used task manager to kill the VS process. I ran VS as administrator once again, and used task manager to kill the process. I then ran VS as I normally would. It took a moment to load the toolbox items, but didn't freeze. I closed VS again, and opened it as I normally would, and it loaded instantly as it normally would.

A: I just ran into this. I do have phone tools installed. For me, it seemed to be caused by a second network connection I have that connects to a device. Disconnecting the device to remove that network connection worked for me.

A: when I go for opening a project in Visual studio 10, then I was getting below status message 
"Loading toolbox content from package 'Microsoft.VisualStudio.IDE.ToolboxControlsInstaller.ToolboxInstallerPackage'" 
This message stay their for 1+ minute & Visual studio goes hang.
To resolve this as per above instruction i follow steps to remove Key from registry key but given registry path was wrong for Windows 8. For Windows 8 correct path is as below
"[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\VisualStudio\10.0\Packages[Registery key no.]"
