Visual Studio 2010 Intellisense slows down everything

I had the same problem with my Windows XP machine. After a long search I found a solution so I'll post it back here since it was the first result I got on google.

Install Windows Automation API update for Windows XP (KB971513).

https://www.catalog.update.microsoft.com/Search.aspx?q=KB971513

It might indicate an issue with the solution's sdf file. Try to close the solution, delete sdf file and load the solution again.