ADSL2+ performance deteriorates over the day

[#1]

Hi all,
I've been on the trial now for about a month and have increasingly noticed that over the course of 24 hours my download speed decays.  On an evening I can have between 10-12 Mbps (based on a My Broadband Speed test) however by the following evening this can be down to > 0.5 Mbps.  The upload speed remains constant at about 371Kbps.  My router reports a decent down sync rate around 15Mbps and an up of 448Kbps whatever the speed test shows.  This problem is immediately corrected by rebooting the modem (Netgear DG834G v2 firmware 3.01.38) after which my speed is back up at the 10-12 Mbps that would be suggested by the down sync rate.
Initially I put this down to the modem training but it's been going on long after the 7-10 days I would have expected.  I can't be sure if this happens slowly or over a short period as I only notice it either end of the day.  I've included a shot from the router stats below.  Any ideas what the cause is or better still the cure?
     

ADSL Link	Downstream	Upstream
Connection Speed	12678 kbps	448 kbps
Line Attenuation	23 db	7 db
Noise Margin	9 db	25 db

Cheers,
-Toenex

[#2]

Not related to your deteriorating download speed but I can see that you have been incorrectly provisioned with a capped upload speed - you should be getting over 1mbps.
You need to send a PM to PM Jameseh.
See http://community.plus.net/forum/index.php/topic,75080.0.html

[#3]

Thanks for that, done.
-Toenex

[#4]

With 23dB you should be around 19mbps.   
What performance do you get from the BT Test Socket?