Hmm... I just got familiar with MONyog and found that W3TC was pulling the DB, getting hung in the process and then causing the server to run out of memory as the PHP processes that were opening to handle the MYSQL requests were freezing while they waited.
Odd because the entire idea of having a DB cache is to not pull from the DB...
But at least I got to familiarize myself with MONyog for the first time.
Oh, the site is was on gets about 15 hits a day... So this was all very odd..
Now it is looking like cronless postie plugin was possibly not compatible with this plugin. Somehow cronless postie got stuck in a loop... Never happened until I installed this plugin.