The system is running. At this point, I've had everything apart, poked at every connector.
I can only assume that the AC supply breaker was loose in it's slot, and that pulling and reseating it was the actual fix. That was the last thing I did, I had been reapplying power and testing from time to time, and I decided to chase back and see if the low voltage reading I got at L1 yesterday was legit or not.
This is the first time I've posted here, but I've gotten a lot of good info with other problems just reading, and some great advice in this thread. Thank you folks for your help, I'll be keeping my fingers crossed that this isn't an intermittent issue.
Thanks!
- Eli