I think the problem might be that if there's a user name, it fails to search the entire post. I typed in a keyword that I knew was in the title of a thread Del Murder had recently posted in (namely 'love' for Bleys' Halifax thread) and typed in 'Del Murder' without the quotes, and it gave me that thread (and even his specific post, if I set it to return results by post). It just seems to only be searching thread titles.

EDIT: Then again, it does seem to work, sometimes. It works if I use wildcards, for instance... Sometimes, still. Not always. Wow, how weird.