Sorry, my fault completely. Part of my theme does customise the BrowserWindow.toolbar file to make it larger, and I discovered that this caused a problem with the new search field. I'm on holiday at the moment though, so I haven't had time to do a blog post about it.
I've posted an update, your best bet is to copy the backup you made of OW (or re-download it) and apply the new version of the theme. It also mucks about a bit with the workspaces window, so let me know if you get any problems with it.
http://www.hicksdesign.co.uk/file_download/20