I think I found a solution - I removed both the personal folders and the archive folders from the search options, and now it works!
Weird...
I have heard many have this problem - the Instant Search just won't work in Outlook 2007 + Vista ( and maybe other operating systems too, but I am using Vista).
I have thousands and thousands of emails, I really need to search through them. Has a solution been found?
Thanks
PS: I have tried all tips I have found on the net

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic