I searched the internet and found there are many reports of the crash when choosing items to add them into toolbox. Of course there are also many suggestions to tackle the problem:
It is suggested the "Power Commands" is the culprit, but I don't have it installed.

It is also suggested to reinstall the custom add-ins. I doubt this would help because I haven't installed many add-ins.

I tried starting Visual Studio in safe mode by launching it form VS command line using "devenv /safemode" then clicked all the tabs. We expect exceptions but there were none. So this approach didn't work.

I also tried to edit "devenv.exe.config" in "C:\Program Files\Microsoft Visual Studio 9.0\Common7\IDE". I thought 'Microsoft.ReportingServices.Interfaces.dll" could be an issue as I couldn't find the assembly's token in Windows registry. I tried setting the tokens to null, it didn't help. I then tried to comment out the dependent assemblies related to this dll in the configuration file and there was no luck either.

I know I cannot afford to reinstall Visual Studio. As the last resort, I tried resetting the toolbox and it worked! The problem is gone. It's so simple. I should do this as the first step to fix the problem.