Sometimes not well-coded extensions/add-ons can cause very annoying error. If you got any error in running Visual Studio 2010, especially if you use lot of 3rd party extensions/add-ons, then running Visual Studio 2010 in Safe Mode will be worth to try.
The Safe Mode will disable all extensions, that way you will know whether the error you got is Visual Studio error or caused by installed extensions.
To run Visual Studio in Safe Mode, you can type devenv.exe /safemode in Visual Studio command line or from Run window.
By default Visual Studio 2010 comes with Intellisense feature enabled. By the way, there are some cases that it’s disabled – can be caused by anything (setting changes on add-in installation, importing settings, human error, your teammate :), etc).
The fix is simple, just open the Tools -> Options, then go to the Text Editor section. Select All Languages or specific language (in this example C#).
Then make sure Auto list members and Parameters information are checked. Click OK and it should be working now.