Newer versions (since 9.6.1, it seems) of BBEdit and TextWrangler for Mac OS X have changed the way the Open File dialogue responds to pressing the Enter key. Pressing Enter on a highlighted directory used to open that directory in the dialogue window, but now it opens a new File Browser instead.
Since I prefer the old behaviour, I end up spending half an hour looking for the command to restore the old behaviour every time I install one of the editors. So, here it is:
defaults write com.barebones.bbedit Misc:AllowFolderSelectionInOpenDialog -bool NO