fact I'm surprised that's changed (FreePBX's DAHDI module created the current config -- i.e. the one I posted in my original email). I'll change that back and see if that makes a difference, but I'm pretty sure I used the above configuration in a previous attempt with the same results. Also, I have indeed received the following messages prior to the interface going down and these errors are what I was initially researching: [root at asterisk-master dahdi]# grep HDLC /var/log/asterisk/full ... [2013-07-30 08:09:03] NOTICE[3621] chan_dahdi.c: PRI got event: HDLC Bad FCS (8) on D-channel of span 1 [2013-07-30 08:09:03] NOTICE[3621] chan_dahdi.c: PRI got event: HDLC Bad FCS (8) on D-channel of span 1 [2013-07-30 08:24:05] NOTICE[3621] chan_dahdi.c: PRI got event: HDLC Bad FCS (8) on D-channel of span 1 [2013-07-30 08:24:05] NOTICE[3621] chan_dahdi.c: PRI got event: HDLC Bad FCS (8) on D-channel of span 1 [2013-07-30 08:29:47] NOTICE[3621] chan_dahdi.c: PRI got event: HDLC Bad FCS (8) on D-channel of span 1 [2013-07-30 08:29:47] NOTICE[3621] chan_dahdi.c: PRI got event: HDLC Bad FCS (8) on D-channel of span 1 [2013-07-30 08:30:52] NOTICE[3621] chan_dahdi.c: PRI got event: HDLC Abort (6) on D-channel of span 1 [2013-07-30 08:30:52] NOTICE[3621] chan_dahdi.c: PRI got event: HDLC Abort (6) on D-channel of span 1 [2013-07-30 08:36:01] NOTICE[3621] chan_dahdi.c: PRI got event: HDLC Bad FCS (8) on D-channel of span 1 [2013-07-30 08:36:01] NOTICE[3621] chan_dahdi.c: PRI got event: HDLC Bad FCS (8) on D-channel of span 1 [2013-07-30 08:39:54] NOTICE[3621] chan_dahdi.c: PRI got event: HDLC Abort (6) on D-channel of span 1 [2013-07-30 08:39:54] NOTICE[3621] chan_dahdi.c: PRI got event: HDLC Abort (6) on D-channel of span 1 A lot of info I found while researching the above error mentioned IRQ's, etc. and was one reason I posted the output of /proc/interrupts, heh...but I'm pretty sure my issue is not one that has to do with the IRQs. Thanks for the suggestions!