looking at the line stats, your margins and sync look fine, the only oddball being the downstream power being at 0, which i'm going to assume is just a broken stat (it happens).
with that said, you do have a good bit of fec errors, but not enough to be causing it to drop from 7 to 1. normally it's odd for it to happen at night (usually happens during the day), but i'd say you have a congestion issue, especially if the stats don't really change between day and night.
pm tim_k
with your dsl number and state you might be having congestion issues, and he'll look into it moreso than either of us (or the usually dumb techs) can.