For anyone who might be interested (after running into the OpenVPN issues i experienced with multiple customer after upgrading both our customers and our own pfSense boxes to 2.5.0:
All the OpenVPN related issues dissappeared "like snow in the sun" after upgrading to 2.5.1 !!
(So, @bennyc i think we can agree that there was an issue... ;) )
However.... a big advice to those who have multiple WAN-connections (wether or not using load-balancing or fail-over mechanism's...) before upgrading to 2.5.1: do not upgrade!!!
Those customers we have with multiple WAN's had serious connectivity-issues (not only over VPN but also from/to the internet) after upgrading from 2.5.0 to 2.5.1!
Rightnow i don't have the time (or desire) to look into this new introduced issue in 2.5.1... i'll just wait for the next patch or major update and have another go with upgrading a multi-WAN customer....