The symptoms of Bug #40614 http://issues.apache.org/bugzilla/show_bug.cgi?id=40614 can be replicated under JVM 1.4.2-02 / Ubuntu Server 6.10 if file ownerships are set incorrectly. Specifically, if you've done a cp -R rather than a cp -pR to copy your Lenya directory or chown'ed -R the whole Lenya directory or critical portions of it. Ownership can also obviously be upset if you're not careful when editing / cp'ing the Lenya source.
Also, the mysterious bug when BXE hangs and requires a browser page refresh is possibly caused by incorrect file ownership / permissions or other errors within the content directory in general (i.e., not necessarily the page you're attempting to edit). It is definitely related to the content.
To do
Identify the ownership / permissions Lenya expects for critical files and record here. Tidy up this page.
(n.b., I used meld to identify diffs between our installation and the original 1.2.4 distribution, and added changes one by one with a server restart and attempted BXE edit each time). BXE worked until bad content was added).