Monitoring plugin since 1.6.1 version has a problem with accessing Statistics and Archiving pages. Shows either a blank page or 404 error. Logs show:
Plugin is reverted to 1.6.0 on the downloads page until the issue is fixed.
The parent plugin for Monitoring is Openfire 4.3.0-SNAPSHOT. I suspect that dropping it to 4.2.0 should do the trick if you want to make it compatible with Openfire 4.2.
Build process has been fixed and since 1.6.2 there is no such issue.