For my personal opinion, for this specific and others related issues, the problem is not WP-DBManager plugin, or W3 Total Cache, but a WordPress core bug regression. Add more cron, freeze WordPress to work correctly. Deleting WP-DBManager, or W3 Total Cache, save more cron core sessions, and WordPress seem to work. WP-DBManager is one of my fovorites plugin, and for me work fine. WP-DBManager author GamerZ is a WordPress guru for me. W3 Total Cache is affected to more bugs and security hole. I have 30 WordPress 3.4.2 installation, on vary host, and, for me, all work fine with WP-DBManager + W3 Total Cache. The only problems is when was upgraded to WordPress 3.5 … WP Crontrol is a very importatnt cool plugin!
@ptnplanet
Your analysis is very accurate ??