Well kilaka you are not alone. 

Since the last (second last?) update on my Nexus S, the Voice Search doesn't find any contacts.  Not even one.  It is the most frustrating thing.  Essentially it's useless.  I can't dial by voice when driving.  That is when I need it the most.

It used to work excellent.  I'd almost say 100%.  Now it is 0%.

I wish I could figure out how to dial back the updates.

Any suggestions would be appreciated.