This happen most times, Search for something and it just freezes and I have to use Ctrl +Alt + Esc to kill it.
Any one else facing it? Disabling nepomuk entries from krunner results fixes it.

Watching System Activity, I found that dbusd was using increasing amounts of CPU - 84% for that one process alone is the highest I saw. Naturally that was causing freezes, and since I spend so much time in Kontact that is where I mostly saw them. Experimentation in launching applications stand-alone found that KMail and Akregator were both affected by this. KAddressbook wasn't. Sheer speculation, but it seems to me entirely possible that this is because my addressbook is akonadi enabled, and therefore using akonadi/nepomuk correctly, while the other two applications are not yet ready.

Like you, I found that disabling nepomuk search in krunner cured my problem completely.

I reported a bug with the same. https://bugs.kde.org/show_bug.cgi?id=224754
Hopefully someone fixes it before 4.4 is launched.