I guess that at this point, any further suggestions would be moot since it's working. I will say that I talked to one of my techs today and he reminded me of a similar issue that we had several years ago. It didn't involve a combo card obviously, but the scenario was similar to yours.

We ended up finding out that Verizon had split the pairs on their punch down to house cable pairs when extending the circuit upstairs to their RJ48X. Basically, the transmit pair ended up being white/blue and orange/white and the receive pair ended up on the blue/white and white/orange. It still managed to work (with service calls every other day) for quite a while. It wasn't entirely the installer's fault, it was the Bell Atlantic cable splicer in 1978 when the riser cables were installed who split the pairs in a splice case. The installer just assumed that pairs 1501 and 1502 were good and didn't bother to check them with anything more than a toner and a probe.

Surprisingly, a T1 or PRI does manage to function (marginally) under these circumstances. I've even seen them continue to function with half of a pair missing, but chock full of errors.

Ed Vaughn, MBSWWYPBX