Ok...
Before the big update a few days ago, DAHDi would only start if I did a service dahdi start, then fwconsole restart. I don't know what version of dahdi & wanpipe I was running at this point, but everything was being kept up to date.
After the big update (which I assume updated the both the kernel and the dahdi & wanpipe drivers?), everything started working correctly for me. At this point my Wanpipe driver was at 7.0.20-9.sng7.
Today the wanpipe drivers were updated to version 7.0.20.13-1.sng7. Having updated these drivers, once again DAHDi will only start if I do a service dahdi start, then fwconsole restart.