Honestly.
If its for a mission critical application, i would ditch it and use a off the shelf solution.
Ive had a nice trixbox setup and running for the past year or so in a residential envirnonment and its been great. (2 VOIP lines, 2 PSTN, 6 IP Extension, 2 ZAP extentions), using the same card as you.
However its not without its days it needs to kicked in the ass and reset.
If you've messed around with it too much, i would reload all settings from scratch and go again.
google "trixbox for dummies" or "trixbox without tears" those are the references i used when setting up my system. The last tittle is paticularly good.
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