Hours of instability .......
I spent many days recording the noise margin "reported" by my Netgear DG834v2 after my circuit became unstable following LLU. What I discovered was that although the device with this chipset (and another brand of modem using the same chipset) would negotiate connection at the defined noise margin, over a matter of 10-20 minutes it would deteriorate until the DSL was unusable. This seemed to be a problem that commenced with ADSL2+. I spent many many hours on the phone to my ISP trying to identify the problem but in the end I concluded the DG834 couldnt cope with a slightly noisy circuit.
I replaced it with a 2Wire 2700 from ebay and all my problems went away.... and came back with the DG834v2.... so I got rid of Mr Netgear's box and since then I've enjoyed a fairly consistent 5mbs + on a 40dB attn line about 2km from the exchange.
How refreshing to see that someone else has identified a similar problem, take heed anyone having probs with this chipset, you could be amazed how quickly the "fault" goes away when you stuff it in the bin!!!!