Downstream SNR gone haywire, IP Profile and sync speed nerfed

[#1]

Hiya all - been a while since I've posted by everything has been gravy.
However I think the week leading up to the bank holiday weekend my daughter was saying she was getting disconnections a lot during the evening - I assumed that was the wifi dropping out at home.
However - cut a long story short, something has happened as my downstream SNR at the time of writing is 23.25dB! It used to be around 14.xxdB - and I did tweak it down to 12. Anyway - router used to Sync at 10mb+, resulting in a minimum IP profile of 9mb. Last I've checked though on speedtester.bt.com - IP profile's at 1.75mb and my router's currently synching at 2,270,500!
So.. I've changed nothing at home. I'm wondering what on earth has happened?
My conn was so stable I'd left it alone for months...
I've (not helped things I know) by trying various things with the router - moving it to different telephone ports, trying different microfilters in case a fault's developed there, tweaking Billion settings but to do avail - it's not connecting at much more than 2mb. Telephone line sounds OK. Bit hissy with a wireless handset but BT's quiet line test is just that with a wired handset in.
Help!
r3fl3x

[#2]

assuming your sync speed is actually 2270 and not 2,270,500 - or is that bits per sec  - then you have been banded

[#3]

Hi r3fl3x,
Jim is on the mark there, it seems you have been banded. Your connection logs since the 30th have been quite awful. The only thing I would say at this point is do do the normal test socket/filter/router checks and raise a fault if it persists.
13:48 03/Sep/2010 N/A   0:36:43 (on going)
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21:43 25/Aug/2010 19:57 30/Aug/2010 4 Days, 22:14:17
Jojo