Hey Stan,
Hate to tell you this, but I'm experiencing the same problem too.
Issue started right after upgrading to 8.5.2.
Selecting remote lists from MLM works just fine, the message previews without issue, but hitting send results in all the messages being delivered without content.
As the previous poster mentioned, if I save the message, quit MBM and then reopen and send the saved message, it is sent OK with content.
This issue is not intermittent and happens every time I try to send a message using MBM and MLM since upgrade to 8.5.2 - I understand from reading this thread that you are having difficulty replicating the issue... I am more than happy to work with you to try and resolve the problem... log files, prefs, settings, tests, etc. Whatever you need.
Best - Anton