Ok, I guess I owe BellSouth an apology. My DSL was working great and suddenly- BAM! I was down to 1/2 my normal speed; it must have been something they did as nothing changed on my side...
After tracing and re-tracing my cables it appears that the fault was in my wiring. Actually not in MY wiring, but the wiring made up my the company that put in the phone override for our alarm system. I traced the phone line (I have another CAT5 dedicated entirely to DSL) and one of the connections to my DSL CPL box was such a bad connection that it snapped off when I touched it.
It has been two years since the alarm company did this install; it is my guess that the cold weather made something contract (perhaps the plywood it is mounted to?) and made the connection bad enough to cause the issues I was seeing.
After a modem and router reboot I am back up to a full 6Mbps- woo hoo!