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.
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).