In my member directory views, if I do a search by Display Name, I get every member returned.  It doesn't matter if there are actually any matching results or not.  Typing an actual display name returns everyone.  Typing a display name that doesn't exist returns everyone.

The only time it doesn't is if I leave it (and all other fields) blank.  In this case, the form just refreshes, no error message or anything.

I have reproduced this, but will need to investigate further.