I tried an old 2wire 2700hgv and it would not connect to Adsl2 / 2+ either.
Line stats from the Netgear
Channel: INTR, Upstream rate = 896 Kbps, Downstream rate = 5120 Kbps
Link Power State: L0
Mode: G.DMT
Channel: Interleave
Trellis: ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 8.9 11.0
Attn(dB): 49.0 24.0
Pwr(dBm): 19.5 12.7
Max(Kbps): 5440 1064
Rate (Kbps): 5120 896
It just won't accept me forcing it to 2 or 2+ at all