There are some issues with the large amount of data indexed for the search and vBB calling all of it up. It seems to be a recurring issue with the new version (3.0.0) of vBB and we're working with them on it. We've increased server memory a great deal which helps alleviate some of the search errors, but depending on what you're searching on, you may end up with a result set so large that it causes vBB to spit out errors.